When a buyer asks an AI for "the best ergonomic chair under $400", the model composes a shortlist of 3–5 products. Either your brand is in that synthesis or it's invisible — there is no page two. Citation share measures how often you make the cut.
It's driven by machine-readable authority: structured data, consistent brand signals, third-party citations, and being crawlable. Cited brands earn disproportionately more clicks per impression than uncited ones.
Ask ChatGPT, Perplexity and Gemini to recommend products in your category and note whether — and where — you appear. Track it monthly; it's the metric that replaces keyword rankings.