Glossary
The GEO glossary.
Plain-English definitions of the terms behind Generative Engine Optimization and AI search.
- Generative Engine Optimization (GEO)
- The practice of making a business eligible to be retrieved and cited by AI assistants such as ChatGPT, Gemini, Claude, and Perplexity. GEO works on the site and across the wider web those engines pull from, since most AI citations are earned off your own domain.
- Answer Engine Optimization (AEO)
- Optimizing content to be the direct answer an engine returns to a question, rather than one of ten blue links. AEO overlaps heavily with GEO; it emphasizes fact-dense answer blocks that map to specific questions users ask.
- Search Engine Optimization (SEO)
- The practice of improving a page's ranking in traditional search results like Google and Bing. SEO optimizes for clicks to a ranked link; GEO optimizes to be quoted inside an AI-generated answer, which often shows no link at all.
- Large Language Model (LLM)
- A model trained on large volumes of text to predict and generate language. LLMs power assistants like ChatGPT, Claude, and Gemini, and are the systems that read retrieved sources and write the answer a user sees.
- Generative engine / AI assistant
- A tool that answers a user's question in natural language instead of returning a list of links. Examples include ChatGPT, Gemini, Claude, and Perplexity. Each reads from a different underlying index, so eligibility must be earned on each surface.
- AI Overview (Google)
- Google's AI-generated summary that appears above the standard search results and draws on Google's index. AI Overviews frequently cite third-party directories, reviews, and community pages rather than a brand's own homepage.
- Retrieval-Augmented Generation (RAG)
- A method where an assistant first retrieves relevant documents from an index, then generates its answer grounded in that retrieved text. RAG is why being present and quotable in an engine's index matters as much as the model itself.
- Citation (in AI answers)
- A source an AI assistant references or links to when producing an answer. Being cited is the core goal of GEO. Muck Rack found that roughly 82% of AI citations come from earned media rather than a brand's own site.
- llms.txt
- A proposed plain-text file at a site's root that offers AI systems a curated, Markdown-friendly map of a site's key content. It is a convention for guiding assistants to the pages a publisher most wants read, distinct from robots.txt, which governs crawler access.
- Structured data / JSON-LD
- Machine-readable markup that states facts about a page, who published it, what a product is, what a term means, in a format engines parse directly. JSON-LD is the format search engines and assistants prefer, embedded in a script tag.
- Schema.org
- A shared vocabulary of types and properties (Organization, Product, FAQPage, DefinedTerm, and more) used to describe web content to machines. It is maintained collaboratively and is the vocabulary most JSON-LD structured data is written in.
- Entity / Entity Trust
- An entity is a distinct thing, a company, person, product, or place, that engines track independently of any single page. Entity Trust is how confidently a system can identify and vouch for that entity, built from consistent, corroborated facts across the web.
- Knowledge Graph
- A structured database of entities and the relationships between them that search engines and assistants use to disambiguate and describe things. A confirmed presence in a Knowledge Graph helps an engine state facts about a business with confidence.
- Wikidata
- A free, collaboratively edited knowledge base of structured data that feeds many Knowledge Graphs and AI systems. A well-formed Wikidata entry is a widely read anchor for an entity's identity and core facts.
- Share of Voice (AI)
- The proportion of relevant AI answers in which a brand is mentioned or cited, measured against competitors. It is a per-engine metric, since the same query can produce different citations in ChatGPT, Gemini, and Perplexity.
- Topical authority / hub-and-spoke
- Topical authority is the depth and coverage that make a site an authority a subject. Hub-and-spoke is a content structure where a central hub page links to focused spoke articles, routing internal authority into the pages that matter most.
- AI crawler (GPTBot, ClaudeBot, PerplexityBot)
- An automated agent that fetches web pages to feed an AI system's index or training. Named crawlers include GPTBot, ClaudeBot, and PerplexityBot. Vercel's analysis of 500 million-plus fetches (Vercel and MERJ) found these crawlers do not execute JavaScript, so client-rendered content is invisible to them.
- Zero-click search
- A search that ends without the user clicking through to any website, because the answer appears on the results page. SparkToro and Similarweb estimated in 2024 that about 60% of Google searches end without a click, a share AI Overviews are expected to raise.
- Directory-gated citation
- A pattern where an engine tends to cite third-party directories, listings, reviews, and community sites rather than a brand's own pages. Google AI Overviews and Perplexity often behave this way, which is why off-site presence drives AI visibility.
- Hallucination
- When an AI assistant states something false or unsupported with apparent confidence. Grounding answers in retrieved, verifiable sources and clear structured data reduces the chance an engine invents or mis-states facts about a business.
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