When an AI grounds an answer about your brand, it links to sources. Cited Pages is the set of unique URLs it pulls from. Your own product pages and docs, plus the third-party pages (retailers, reviews, roundups, forums) the engines lean on.
It answers two useful questions at once: which of your own pages are doing the work (so you can double down on them), and which third-party pages the engines trust in your category (so you know where earned coverage actually moves the needle). Often the most-cited pages aren't yours at all, which is exactly the signal that you need to get included in those independent sources.
One counting note: a URL cited by several engines is still one unique page, so per-engine counts can sum higher than the overall unique total. Read alongside Citation Coverage, which turns this into a percentage.