REFERENCE

AI Glossary A–Z

Clear definitions of 143 AI terms, with a link to the full explanation where one exists.

A

A2A (Agent2Agent)
An open protocol for communication between independent AI agents: discovering capabilities, delegating tasks and returning results. It complements MCP, which connects agents to tools. Details are version-dependent.
Agent (AI agent)
A system in which a model pursues a goal by repeatedly choosing actions, calling tools and reading the results until it finishes or hits a limit.
Agentic workflow
A designed process that combines model calls, tools, checks and sometimes humans along a path the developer defines, as opposed to a model freely choosing every step.
AI (Artificial Intelligence)
The broad field of building software that performs tasks normally associated with human judgement, such as perception, language and decision-making.
Alignment
Work to make AI systems behave in line with human intentions and values, including being helpful, honest and safe. Training steps such as instruction tuning and preference tuning contribute to it.
API key
A secret string a program sends to an API to identify itself. Anyone who has the key can call the API as that program, so it belongs on a server, not in a browser.
Approximate nearest neighbour (ANN)
A family of search methods that quickly find vectors that are very likely, though not guaranteed, to be the closest to a query. Used by vector databases to stay fast at scale.
Attention
The mechanism in a transformer that lets each token weigh how relevant every other token is when building its representation.
Authorization code flow
The usual OAuth 2.0 flow for user login: the browser gets a short-lived code, and the server exchanges that code for tokens. Public clients add PKCE so a stolen code is not enough.

B

Backpropagation
The algorithm that computes how each parameter contributed to the loss, so gradient descent can update it.
Benchmark
A standard test used to compare models on a defined task. Useful for rough comparison, but not a substitute for testing on your own use case.
Best-of-N sampling
Generating several candidate answers and returning the one a scorer — tests, a verifier or a reward model — rates highest.

C

C# (C sharp)
A statically typed language on .NET, commonly used for APIs, workers and Azure services in Microsoft-centred stacks.
C2PA (Content Credentials)
An open standard for cryptographically signed provenance metadata describing how media was made and edited, including AI generation.
Chain of thought
A prompting technique in which the model is encouraged to work through intermediate reasoning steps before giving its answer. Its usefulness varies by model and task.
Chatbot
Software that converses with users. Modern chatbots are usually powered by LLMs; the word says little about whether the system can take actions.
Chunking
Splitting documents into smaller passages so each can be embedded and retrieved on its own, as in RAG.
Constitutional AI
A training approach in which a model critiques and revises its outputs against written principles, with AI-generated preference labels (RLAIF) used for further training.
Constrained decoding (guided generation)
Restricting a model's next-token choices at each step so output must follow a schema, regex or grammar. It guarantees well-formed output, not correct content.
Container
A process isolated with its own filesystem view, built from an image and run by a container runtime. It shares the host kernel, unlike a virtual machine.
Context engineering
Curating everything a model sees each turn — instructions, retrieved facts, memory, tool definitions and results — so agents stay reliable.
Context window (context length)
The maximum amount of text, measured in tokens, a model can consider in one request, covering instructions, conversation, documents and the reply.
Contrastive learning
Training that pulls matching pairs (such as an image and its caption) together in embedding space and pushes non-matching pairs apart. CLIP is a well-known example.
CORS (Cross-Origin Resource Sharing)
A browser check that asks a server whether a page from another origin may read the response. It is not authentication, and non-browser clients ignore it.
Cosine similarity
A measure of how closely two vectors point in the same direction. It is widely used to compare embeddings: values near 1 mean very similar, near 0 mean unrelated.

D

Deep learning
Machine learning that uses neural networks with many layers. It underlies most modern vision, speech and language models.
Diffusion model
A generative model, common in image generation, that starts from random noise and refines it step by step into content matching a prompt.
Direct Preference Optimization (DPO) (DPO)
A preference-optimization method that tunes a model directly on chosen-versus-rejected response pairs relative to a reference model, without a separate reward model or RL loop. It is an alignment technique, not ordinary reinforcement learning.
Distillation (knowledge distillation)
Training a smaller student model to imitate a larger teacher model's outputs, yielding a cheaper model for narrower tasks.

E

Embedding
A list of numbers (a vector) that represents the meaning of content so that similar items are close together. Basis of semantic search and RAG.
Embodied AI
AI that perceives and acts in the physical or simulated world through a body such as a robot arm, drone or vehicle.
Entra ID (Microsoft Entra ID, Azure AD)
Microsoft's cloud identity service, formerly Azure Active Directory. It signs users in and issues tokens for Microsoft 365, Azure and registered apps.
EU AI Act
The European Union's risk-based regulation of AI systems, Regulation (EU) 2024/1689. Application dates are phased; verify the current timetable.
Evals (evaluations)
Structured tests that measure how well an AI system performs on tasks you care about, using test cases, graders and tracked scores.
Express
A small Node.js library for HTTP routes and middleware. It does not include a database or a front end.

F

Few-shot prompting
Including a small number of example inputs and outputs in the prompt to show the model the pattern you want. Zero-shot means giving no examples.
Fine-tuning
Further training a pre-trained model on your own examples so it adopts a consistent behaviour, format or skill.
FlashAttention
An exact attention algorithm that tiles computation to cut memory traffic, speeding up transformers and enabling longer sequences without approximating the result.
Foundation model
A large model trained on broad data that can be adapted to many tasks. Large language models are the best-known example.
Function calling (tool calling)
A model-API feature in which the model returns a structured request to run a named function with arguments. Your code runs it and returns the result.

G

Generative AI
AI that produces new content such as text, images, audio, video or code.
GGUF
A model file format used by llama.cpp, supporting many quantisation levels and bundling metadata for local inference.
Git
A distributed version-control system that records snapshots of a project so you can branch, merge and recover history.
Graph neural network (GNN)
A neural network that learns on graph-structured data by passing messages between connected nodes, used for molecules, networks and some weather models.
GraphQL
An API style in which the client names the fields it wants and the server resolves them against a schema. Not the same thing as Microsoft Graph.
GraphRAG
Retrieval that builds a graph of entities and relationships (often with community summaries) so questions needing connections or corpus-wide synthesis can be answered.
Grounding
Tying a model's answer to supplied source material or tool results so claims can be traced and checked.
GRPO (Group Relative Policy Optimization)
A PPO-style reinforcement-learning method that normalises rewards within a group of sampled outputs per prompt, avoiding a separate value model. Used for training on tasks with verifiable rewards.
Guardrails
Checks and limits around an AI system, such as input filters, output validation, permission limits and human approvals, that reduce harmful or unwanted behaviour.

H

Hallucination
Fluent, confident model output that is false, unsupported by the sources, or invented, such as fake citations or facts.
Hugging Face (HF)
A hub and set of libraries for publishing and loading machine-learning models and datasets, including the transformers library.
Human in the loop
A design in which a person reviews or approves AI output or actions at defined points, especially before high-impact or irreversible steps.

I

Inference
Running a trained model to produce output for new input, as opposed to training it.
Instruction tuning
Additional training that teaches a pre-trained model to follow instructions and respond helpfully, turning a text predictor into an assistant.

J

Jailbreak
An attempt to get a model to break its safety rules through crafted input. Related to, but distinct from, prompt injection.
JSON Web Token (JWT)
A signed token whose payload is JSON. The payload is readable by anyone; trust comes only from checking the signature, issuer, audience and expiry.

K

Knowledge cut-off
The point after which a model's training data contains no information. Later events are unknown to it unless supplied via the prompt, search or tools.
KV cache
Stored attention keys and values for earlier tokens, reused during generation to avoid recomputation. It speeds decoding but grows with context length and batch size.

L

LangChain
A framework for composing model calls, tools and retrieval in Python or JavaScript. It is optional glue, not a model.
llama.cpp
A C/C++ inference engine for running quantised models on CPUs and consumer GPUs using the GGUF format.
LlamaIndex (Llama Index)
A framework focused on loading documents, indexing them and retrieving context for a language model.
LLM (Large Language Model)
A very large neural network trained on text to predict the next token, enabling writing, summarising, translation, question answering and code generation.
LLM observability
Recording prompts, retrieved context, tool calls, outputs, latency and cost to debug and improve AI applications, while protecting sensitive data in those records.
LLM-as-a-judge
Using a language model to grade or compare other outputs against a rubric. It scales evaluation but has biases and needs calibration against human judgement.
Local AI
Running models on hardware you control instead of a hosted service, so data need not leave your device.
LoRA (low-rank adaptation)
A parameter-efficient fine-tuning method that trains small add-on matrices while the original model stays frozen, greatly reducing training cost.

M

Machine learning
The part of AI in which systems learn patterns from data rather than following hand-written rules.
MCP (Model Context Protocol)
An open protocol for connecting AI applications to external tools, data and prompts through servers that clients can discover and call.
MCP client
The component inside an AI host application that holds a connection to one MCP server and relays requests and results.
MCP server
A program that exposes tools, resources and prompts to MCP clients, often wrapping an existing API, database or file system.
Mechanistic interpretability
Research that tries to explain model behaviour by analysing internal components such as features and circuits.
Memory (agent)
Information a system stores outside the model and re-inserts into the prompt, such as recent messages, summaries and durable facts, because models themselves retain nothing between requests.
Microsoft 365 (M365, Office 365)
Microsoft's cloud suite for mail, files, SharePoint and Teams. Office 365 is the older name for the same tenant story.
Microsoft Graph
The REST API at graph.microsoft.com for Microsoft 365 data such as users, mail, files, sites and Teams. It is not GraphQL.
Mixture of experts (MoE)
A model design with many specialist sub-networks and a router that activates only a few per token, so total parameters exceed active parameters.
MMLU
A multiple-choice benchmark across 57 subjects used to compare breadth of knowledge in language models; now close to saturated for top models.
Model card
A structured document describing a model's intended use, training data, evaluation, limitations and ethical considerations.
Model drift (data drift, concept drift)
Degradation of a deployed model's performance as input data or the relationship between inputs and outcomes changes over time.
Multi-agent system
A setup in which several model-driven agents with distinct roles or contexts cooperate on a larger task.
Multimodal
Able to handle more than one type of data, such as text together with images or audio.

N

Neural network
A model made of layers of simple connected units whose strengths (parameters) are adjusted during training. The basis of deep learning.
Next.js
A React framework that adds routing and a server runtime so secrets and data fetching can stay off the browser.

O

OAuth 2.0 (OAuth)
A protocol for granting an application limited access to an API without sharing the user's password. OpenID Connect adds sign-in identity on top.
Open weights
Models whose trained parameters are published for download and local use, subject to the licence. Not always the same as fully open source.
OpenID Connect (OIDC)
An identity layer on OAuth 2.0. The ID token says who signed in. The access token is what you send to an API.
ORM (object-relational mapper)
A library that maps database rows to objects in a programming language. Prisma is one TypeScript example. The SQL still runs.
ORM (outcome reward model)
A scorer that judges only the final answer of a reasoning attempt. Not to be confused with an object-relational mapper in software.
Overfitting
When a model or prompt works well on the examples used to build it but poorly on new cases. Held-out test data helps detect it.

P

Parameters (weights)
The numbers inside a model that are adjusted during training and determine its behaviour. Model size is often quoted as a parameter count.
Perplexity
A language-modelling metric reflecting how well a model predicts text; lower means less "surprised". It is not a measure of usefulness or truth.
Positional encoding
Information added so a transformer knows token order; methods include sinusoidal encodings, RoPE and ALiBi.
PostgreSQL (Postgres, PG)
An open-source relational database. Applications talk to it with SQL. The pgvector extension can store embeddings in the same server.
Power Platform
Microsoft's low-code family: Power Apps, Power Automate, Power BI and Dataverse, used for tenant workflows beside Microsoft 365.
PPO (Proximal Policy Optimization)
A widely used reinforcement-learning algorithm that clips policy updates to keep training stable; used in RLHF pipelines.
Pre-training
The initial, large-scale training stage in which a model learns general patterns from broad data before any specialised adaptation.
Preference optimization
The family of methods that tune models using comparisons of better versus worse responses — RLHF, DPO, KTO, IPO, ORPO, SimPO and relatives.
PRM (process reward model)
A scorer that rates each intermediate step of a reasoning chain, enabling step-level feedback and guided search.
Prompt
The input given to a model: instructions, context, examples and the user's request.
Prompt caching
Reusing computation for a repeated prompt prefix to cut latency and often cost. Rules and pricing are provider-specific.
Prompt injection
An attack where text supplied to a model, directly or hidden in content it reads, tries to override the developer's instructions.

Q

Quantisation
Storing a model's parameters at lower numeric precision to cut memory use, usually at some cost in quality.

R

RAG (Retrieval-Augmented Generation)
Retrieving relevant passages from your data and giving them to a model so its answer is based on that material.
Reasoning model
A language model trained or configured to work through a problem in intermediate steps before answering, trading latency and cost for accuracy on multi-step tasks.
Red teaming
Structured adversarial testing of an AI system to find failures, misuse paths and vulnerabilities before real attackers or users do.
Redis
An in-memory store for keys, expirations, counters and short-lived coordination. Best used as a cache or rate limiter beside a durable database.
Reinforcement learning (RL)
Learning to choose actions to maximise cumulative reward through trial and feedback. Preference methods such as DPO are classified separately as preference optimization.
Reranking
A second, more precise scoring step that reorders retrieved candidates before they are given to the model.
Reward hacking
When a system exploits flaws in its reward signal, scoring highly without doing what was intended.
RLAIF (reinforcement learning from AI feedback)
Training with preference labels generated by an AI model, guided by written principles, instead of human labels.
RLHF (reinforcement learning from human feedback)
A training approach that uses human preference judgements to steer a model towards responses people rate as better.
RLVR (reinforcement learning from verifiable rewards)
Reinforcement learning where rewards come from automatic checkers such as exact answer match or unit tests, used to train reasoning behaviour.

S

Sampling
The step where the next token is chosen from the model's probabilities. Settings such as temperature control how predictable or varied the choice is.
Scaling laws
Empirical relationships showing how model loss tends to improve predictably with parameters, data and compute.
Self-consistency
Sampling several reasoning attempts and choosing the final answer most of them agree on.
SharePoint
Microsoft 365's platform for sites, document libraries, lists and intranet pages. Modern custom web parts are built with the SharePoint Framework.
SharePoint Framework (SPFx)
Microsoft's TypeScript toolchain for client-side SharePoint web parts and extensions. The usual UI library is React.
Small language model (SLM)
A compact language model, typically up to a few billion parameters, that runs cheaply and can be strong on narrow tasks.
Speculative decoding
Speeding up generation by letting a small draft model propose tokens that a large model verifies in parallel, preserving the large model's output distribution.
SPFx (SharePoint Framework)
The short name for the SharePoint Framework, used to build client-side SharePoint web parts and extensions with TypeScript, usually with React.
State space model (SSM)
A sequence model that carries a compact recurrent state, giving linear-time processing as an alternative to attention; Mamba is a well-known example.
Structured output
Model output constrained to a defined format, such as JSON matching a schema, so software can use it directly.
Sycophancy
A model's tendency to tell users what they want to hear — agreeing with mistaken claims or flattering them — rather than what is accurate.
System prompt
Standing instructions from the developer that define a model's role, rules and format across a conversation, separate from the user's messages.

T

Temperature
A setting that controls randomness when a model picks the next token. Lower values give more predictable output; higher values give more varied output.
Test-time compute (inference-time scaling)
Spending extra computation when answering — longer reasoning, multiple samples, search or verification — to improve hard answers.
Thinking budget (reasoning effort)
A provider setting that caps or tunes how much reasoning a model does per request. Names and semantics vary by provider.
Token
The unit of text a model reads and writes: a word, part of a word, or punctuation. Limits and prices are commonly measured in tokens.
Tokenizer
The component that splits text into tokens and maps them to numbers. Different model families use different tokenizers.
Tool (agent tool)
A described capability, such as search, a database query or an API call, that a model can request and that your code executes.
Training
The process of adjusting a model's parameters using data so its outputs improve on a target task.
Transformer
The neural-network architecture, introduced in 2017, behind most modern language models. Its key feature is attention.
TypeScript (TS)
JavaScript with a static type system. The compiler emits plain JavaScript. SharePoint Framework projects are TypeScript-first.

V

Vector
An ordered list of numbers. In AI, embeddings are vectors, and closeness between vectors reflects similarity in meaning.
Vector database (vector store)
A system that stores embedding vectors with metadata and finds the closest matches to a query vector quickly.
Vision Transformer (ViT)
A transformer that splits an image into patches treated as tokens, matching or beating CNNs at scale.
Vision-language model (VLM)
A model that takes images (and often video) with text and produces text: descriptions, answers about charts and screenshots, visual reasoning.
VLA (vision-language-action model)
A model that maps camera images and a language instruction to robot actions, extending vision-language models to control.
vLLM
An open-source LLM serving engine known for paged KV-cache memory and continuous batching.

W

Webhook
An HTTP callback: another system POSTs to your URL when an event happens. Verify the signature and treat retries as normal.
World model
A learned model of how an environment evolves in response to actions, used for planning, imagination-based training or generated simulation.

Z

Zero-shot prompting
Asking a model to perform a task with instructions only and no examples.