The GEO glossary

Generative Engine Optimization (GEO) is the practice of measuring and improving how AI answer engines — ChatGPT, Perplexity, Gemini, Google AI Overviews, AI Mode, and Copilot — represent a brand: whether they name it and cite its domain when buyers ask category questions.

Answer Engine Optimization (AEO) is optimizing to be the source an AI answer engine draws from and names when it responds to a question, rather than optimizing for a ranked list of links. In practice AEO and GEO describe the same output-side goal.

An answer engine is an AI system that responds to a question with a synthesized answer instead of a list of links — for example ChatGPT, Perplexity, Gemini, Google AI Overviews, Google AI Mode, and Microsoft Copilot. It may name brands in the answer and cite sources beneath it.

Mention and citation are two independent booleans read from one AI answer. Mention asks whether the brand is named in the answer text the reader sees; citation asks whether the brand’s own domain appears among the cited sources. An answer can do either, both, or neither.

A conversion gap is when an AI answer cites a brand’s own domain as a source but never names the brand in the answer. The reader absorbs the content and credits the AI; the brand did the work and stayed invisible.

A source gap is when an AI answer names a brand but cites someone else’s domain — a review site, competitor, or directory — as the source. The reader hears the brand’s name and clicks through to another site to learn more.

Evidence, not a score is the principle that every number in an AI-visibility report must open back to the raw material it came from — the verbatim answer, its cited sources, and the run metadata — instead of a sealed, black-box composite the client has to trust.

Query fan-out is when an answer engine expands a single user question into several related sub-queries, retrieves for each, and synthesizes the results into one answer. It means one visible question can pull from many different sources — and name different brands than the literal query implies.

AI share of voice is how often a brand is named (and cited) across a fixed set of category prompts and engines, relative to its competitors. Unlike a single visibility score, it is only meaningful when each count opens back to the stored answers behind it.

A GEO audit runs the real questions a brand’s buyers ask through the AI answer engines, captures the verbatim answers and cited sources, and scores each on two booleans (named, cited) to map where the brand is a stronghold, has a gap, or is absent.