Glossary
AI search, defined.
The terms you will meet when working on visibility in ChatGPT, Gemini, Perplexity and Google's AI results, in plain English.
Answer Engine Optimization (AEO)
The practice of making a brand's content, structured data and off-site presence easy for AI answer engines such as ChatGPT, Gemini, Perplexity and Google AI Overviews to find, trust and cite in their answers.
Generative Engine Optimization (GEO)
A near-synonym for AEO used in academic and industry writing: optimizing content so generative AI systems include and attribute it when they compose an answer.
Answer engine
A search experience that replies with a composed answer instead of a list of links — for example ChatGPT search, Perplexity, Gemini or Google AI Mode.
AI Overview
Google's AI-generated summary shown above organic results for some queries, with links to the sources it drew on.
Citation
A link or source attribution an AI engine shows alongside its answer. Being cited means the engine used your page as evidence.
Brand mention
An AI answer naming your brand, with or without linking to your site. Mentions shape which brands buyers consider; citations show which pages the engine relied on.
Prompt tracking
Running a fixed set of buyer-style questions through AI engines on a schedule and recording which brands, claims and sources appear, so changes can be measured over time.
Grounding
When an AI model retrieves live web or search results and bases its answer on them, rather than answering only from what it learned in training.
Retrieval-augmented generation (RAG)
A technique where a model first retrieves relevant documents and then generates an answer from them. Most answer engines use some form of RAG, which is why crawlable, well-structured pages matter.
llms.txt
A markdown file at the root of a site (/llms.txt) that gives AI systems a concise summary of the site and links to its most important pages, proposed at llmstxt.org.
Structured data (schema markup)
Machine-readable JSON-LD that describes a page's entities — an Organization, Article, Product or FAQ — using the schema.org vocabulary, so search and AI systems do not have to infer them.
Entity
A uniquely identifiable thing — a company, person, product or place — that search engines and AI models track in their knowledge graphs, independent of the words used to describe it.
Knowledge graph
A database of entities and the relationships between them. Google's Knowledge Graph and Wikidata are the best known; AI engines lean on them to decide what a brand is.
sameAs
A schema.org property listing a brand's or person's profiles elsewhere (LinkedIn, Wikidata, YouTube), which helps engines connect them into one entity.
Search Engine Optimization (SEO)
Improving a site's visibility in traditional search results through technical health, content that matches search intent, and links and mentions from other sites. Most AEO work builds on the same foundations.
AI search optimization
An umbrella term for improving how a brand appears in AI-generated results — ChatGPT, Gemini, Perplexity and Google's AI Overviews and AI Mode — covering both AEO and GEO practices.
E-E-A-T
Experience, Expertise, Authoritativeness and Trustworthiness — the quality signals described in Google's search quality rater guidelines, such as named authors and clear sourcing.
AI crawlability
Whether AI and search crawlers such as GPTBot, ClaudeBot, PerplexityBot and Googlebot can fetch and read a page — governed by robots.txt, server responses and how much content is rendered without JavaScript.
Content signals
A robots.txt directive (Content-Signal) stating whether content may be used for search, as AI answer input, or for AI training.
Query fan-out
When an AI engine splits one question into several sub-queries, searches each, and combines the results. Pages that answer those sub-questions directly are more likely to be cited.
Zero-click search
A search where the user gets what they need from the results page or AI answer without clicking through to a website.