# AI Search Glossary

Definitions of the terms behind AI search, from answer engine optimization to retrieval-augmented generation, and what each one means for whether AI engines recommend your brand.

- [Agentic commerce](https://www.searchable.com/glossary/agentic-commerce): Agentic commerce is shopping in which an AI agent acts for a person: it finds and compares products and can complete the purchase, sometimes without the shopper opening the merchant's website. Open protocols such as the Agentic Commerce Protocol from OpenAI and Stripe and Google's Universal Commerce Protocol give agents and merchants a shared way to handle the order.
- [AI brand mentions](https://www.searchable.com/glossary/ai-brand-mentions) (also called LLM brand mentions, mention rate): AI brand mentions are the times an AI engine like ChatGPT or Google AI Overviews names your brand in an answer. A mention counts whether or not the answer links to your website. That's the difference from a citation, where the engine credits a specific page as its source.
- [AI brand monitoring](https://www.searchable.com/blog/ai-brand-visibility-tracking) (also called AI search monitoring): Keeping watch on what AI engines say about your brand and which sources they draw on when they say it.
- [AI brand sentiment](https://www.searchable.com/blog/ai-brand-sentiment): The tone an AI engine takes when it describes your brand: positive, neutral, or negative, and the specific claims behind that tone.
- [AI citations](https://www.searchable.com/glossary/ai-citations) (also called citation frequency, citation rate, LLM citations): AI citations are the links an AI engine attaches to its answer to show which web pages the information came from. Each citation credits a specific URL. A brand mention is different: the engine names a company in the text, even when it doesn't link to that company's site.
- **AI crawlers** (also called AI bots, LLM crawlers): Bots run by AI companies that fetch web pages, either to collect training data or to retrieve live sources for an answer.
- **AI hallucination** (also called hallucination): A confident but false statement from an AI model, such as a price your product never had or a source that doesn't exist.
- [AI referral traffic](https://www.searchable.com/glossary/ai-referral-traffic) (also called LLM referral traffic, AI traffic): AI referral traffic is website visits that arrive when someone clicks a link inside an AI-generated answer, such as a cited source in ChatGPT, Perplexity, Gemini, Claude, or Microsoft Copilot. Analytics tools identify it by the referring domain or by a UTM tag, like the utm_source=chatgpt.com parameter ChatGPT adds to its links.
- [AI search optimization](https://www.searchable.com/blog/ai-search-optimisation-guide) (also called AI SEO): The umbrella term for improving how a brand appears across AI search surfaces, from ChatGPT and Perplexity to Google AI Overviews and AI Mode.
- [AI share of voice](https://www.searchable.com/glossary/ai-share-of-voice) (also called AI SOV, share of voice in AI search): AI share of voice is the percentage of all brand mentions in AI-generated answers that belong to your brand, measured across a fixed set of prompts. Each brand counts once per answer it appears in. If brands are named 200 times across your tracked answers and 50 of those mentions are yours, your share of voice is 25%.
- [AI visibility](https://www.searchable.com/blog/improve-ai-brand-visibility) (also called AI search visibility, AI brand visibility): How often AI engines bring up your brand when people ask about your category, and how accurately they describe it.
- [AI visibility score](https://www.searchable.com/glossary/ai-visibility-score): An AI visibility score is the percentage of tracked AI answers that mention your brand. You divide the answers that name you by every answer in your tracked prompt set, including answers that name no brand at all. If your brand appears in 30 of 100 tracked answers, your AI visibility score is 30%.
- [AI visibility tracking](https://www.searchable.com/blog/ai-visibility-tracking): Measuring AI visibility over time by running the same prompts across engines and comparing mentions, citations, and positions from run to run.
- **Answer engine** (also called AI answer engine): A search tool that replies with a written answer instead of a list of links. ChatGPT, Perplexity, Gemini, and Google AI Overviews are all answer engines.
- [Answer engine optimization (AEO)](https://www.searchable.com/blog/what-is-aeo) (also called AEO): The practice of making your brand and content easy for AI answer engines to find and cite when they answer a question.
- [Branded vs unbranded prompts](https://www.searchable.com/glossary/branded-vs-unbranded-prompts) (also called branded prompts, unbranded prompts, non-branded prompts): Branded prompts are AI questions that name your company, such as "Is Acme good for agencies?" Unbranded prompts describe a need without naming any brand, such as "best project software for agencies." Tracking unbranded prompts shows whether AI engines recommend you to buyers who don't know you yet.
- [ChatGPT](https://www.searchable.com/blog/where-does-chatgpt-get-its-data): OpenAI's AI assistant. It answers from its training data and, when search is used, from live web results it retrieves and cites.
- [ChatGPT Shopping](https://www.searchable.com/blog/how-to-get-product-listed-chatgpt-shopping-guide): Product results inside ChatGPT answers, shown as cards with images, prices, and links to merchants.
- **Claude**: Anthropic's AI assistant. It can search the web and cite sources when a question needs current information.
- [Content chunking](https://www.searchable.com/glossary/content-chunking) (also called chunking, passage ranking, passage slicing): Content chunking is the way AI search systems split a web page into smaller passages so each one can be retrieved and quoted on its own. The term also describes writing pages in clear, self-contained sections, so any passage an engine pulls out still makes sense without the rest of the page.
- [Content freshness](https://www.searchable.com/blog/content-freshness-signals): Signals that tell search engines and AI systems a page is current, such as a visible update date and recent data.
- **Context window**: The maximum amount of text, measured in tokens, that a model can consider at once, including the prompt, any retrieved sources, and its own reply.
- **Conversational search**: Searching by asking questions in natural language and refining them through follow-ups, with the engine keeping the context of the conversation.
- **Domain authority**: A score created by Moz that estimates how likely a domain is to rank, based mostly on its backlinks. It's a third-party metric that Google doesn't use.
- [E-E-A-T](https://www.searchable.com/blog/e-e-a-t) (also called EEAT, experience, expertise, authoritativeness, trustworthiness): Experience, expertise, authoritativeness, and trustworthiness: the qualities Google's quality rater guidelines use to judge whether content deserves to be trusted.
- **Earned media**: Coverage of your brand on sites you don't own, such as reviews, press, forums, and third-party lists. AI engines lean heavily on these sources when they recommend brands.
- [Embeddings](https://www.searchable.com/glossary/embeddings) (also called vector embeddings): Embeddings are lists of numbers that represent the meaning of a piece of content, such as a paragraph of text or an image. Content with similar meaning gets similar numbers, so a system can find a relevant passage even when it shares no words with the question. Embeddings are what make semantic search and AI retrieval work.
- **Entity SEO** (also called entity optimization): Making sure search engines and AI models recognize your brand as a distinct entity, with consistent facts about what it is and what it's connected to.
- **Featured snippet**: A highlighted excerpt from one web page that Google shows near the top of the results to answer a query directly.
- **Gemini**: Google's family of AI models and the name of its standalone AI assistant. Gemini models also power AI Overviews and AI Mode.
- **Generative engine optimization (GEO)** (also called GEO): Optimizing content to be included and credited in answers written by generative AI systems. In practice the term is used almost interchangeably with AEO.
- [Google AI Mode](https://www.searchable.com/blog/google-ai-mode) (also called AI Mode): A conversational search mode inside Google Search that answers with an AI-written response and supports follow-up questions.
- [Google AI Overviews](https://www.searchable.com/blog/rank-in-ai-overviews) (also called AI Overviews, AIO): AI-generated summaries that appear above the organic results in Google Search, with links to the pages they draw on.
- **GPTBot** (also called OAI-SearchBot, ChatGPT-User): OpenAI's crawler for collecting model training data. ChatGPT search uses a separate crawler, OAI-SearchBot, so blocking GPTBot in robots.txt doesn't remove you from ChatGPT search results.
- [Grounding](https://www.searchable.com/glossary/grounding) (also called grounding in AI): Grounding in AI means tying a language model's answer to specific source material, such as live search results or a company's own documents, so the model isn't relying only on what it learned in training. A grounded answer can point to its sources, which is why AI search engines show citations.
- **Hybrid search**: Retrieval that combines keyword matching with vector search, so results match both the exact terms and the meaning of a query.
- **Knowledge cutoff** (also called training cutoff): The date after which a model has no training data. Anything newer reaches the model only if it retrieves it from the web at answer time.
- **Knowledge graph**: A database of entities and the relationships between them. Google's Knowledge Graph powers knowledge panels and helps AI systems resolve which brand a question is about.
- **Large language model (LLM)** (also called LLM): An AI model trained on large amounts of text to predict and generate language. LLMs are the engines inside ChatGPT, Claude, Gemini, and most AI search tools.
- [LLM SEO](https://www.searchable.com/blog/llm-seo) (also called LLM optimization, LLMO): Search optimization aimed at large language models, covering both your own pages and the third-party sources models draw on when they mention you.
- [llms.txt](https://www.searchable.com/glossary/llms-txt): llms.txt is a proposed standard for a markdown file at a website's root (example.com/llms.txt) that summarizes the site and links to its most useful pages for language models. Jeremy Howard of Answer.AI proposed it in September 2024. Google says its search ignores the file, and no other major AI search engine has said it uses one.
- **Microsoft Copilot** (also called Copilot): Microsoft's AI assistant, built into Windows, Edge, Bing, and Microsoft 365. It grounds web answers in Bing search results.
- [Model Context Protocol (MCP)](https://www.searchable.com/glossary/model-context-protocol) (also called MCP): The Model Context Protocol (MCP) is an open standard for connecting AI applications to outside tools and data. An MCP server describes what it can do in a format any MCP-compatible assistant understands, so one integration can work across AI apps like Claude and Cursor without custom code for each.
- **Perplexity**: An AI answer engine that searches the web for every query and shows numbered citations beside its answer.
- [Prompt tracking](https://www.searchable.com/glossary/prompt-tracking) (also called tracked prompts, prompt monitoring): Prompt tracking is running a fixed set of buyer questions through AI engines like ChatGPT and Perplexity on a schedule, then recording which brands and sources appear in each answer and where they rank. Comparing the same prompts over time shows whether your AI visibility is rising or falling.
- [Query fan-out](https://www.searchable.com/blog/what-is-query-fanout-aeo-glossary) (also called query fanout, fan-out queries): When an AI engine splits one question into several related searches, retrieves results for each, and combines them into a single answer.
- [Retrieval-augmented generation (RAG)](https://www.searchable.com/glossary/retrieval-augmented-generation) (also called RAG): Retrieval-augmented generation (RAG) is a technique where an AI model first searches a set of documents for passages that match a question, then writes its answer from those passages. Because it looks things up at answer time, the model can use up-to-date information and point to where it came from.
- **Search Generative Experience (SGE)** (also called SGE): Google's 2023 Search Labs experiment with AI-generated answers. It became AI Overviews when Google rolled the feature out in May 2024.
- [Semantic search](https://www.searchable.com/glossary/semantic-search): Semantic search is a way of finding information by matching the meaning of a query instead of its exact words. It lets a search engine or AI assistant return a page about "affordable CRM for startups" when someone asks for a "cheap customer database for a new company," even though the two phrases share almost no words.
- **Server-side rendering (SSR)** (also called SSR, client-side rendering, CSR): Building a page's HTML on the server before it is sent, so crawlers that don't run JavaScript, including most AI crawlers, can still read the content.
- **Structured data** (also called schema markup, schema.org): Code, usually schema.org JSON-LD, that labels what a page contains, such as a product or an FAQ, in a format machines can parse.
- [Tokenization](https://www.searchable.com/blog/what-is-tokenisation) (also called tokens): Breaking text into tokens, the small units of words and characters that language models read and generate.
- **Topical authority**: How thoroughly a site covers a subject, judged across all its pages rather than any single one.
- [Universal Commerce Protocol (UCP)](https://www.searchable.com/blog/what-is-universal-commerce-protocol-ucp) (also called UCP): An open standard backed by Google that lets AI agents discover products and complete purchases with merchants through a common interface.
- **Vector search**: Finding documents by comparing their embeddings with the embedding of a query, returning the closest matches in meaning.
- [WebMCP](https://www.searchable.com/blog/what-is-webmcp): A proposed web standard that lets a website expose actions, such as search or checkout, as tools an in-browser AI agent can call directly.
- [XML sitemap](https://www.searchable.com/blog/what-is-an-xml-sitemap): A file that lists the URLs on a site you want search engines to crawl, often with the date each was last changed.
- [Zero-click search](https://www.searchable.com/blog/zero-click-optimisation): A search that ends without a click to any website, because the answer is shown directly on the results page or in an AI response.

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