There's a difference between an AI mentioning your brand and citing your own pages as the evidence. Citation Coverage measures the second: of the answers that mention you, how often the engine also links your own domain as a source.
It's a trust-and-grounding signal. High coverage means the AI is pulling from your content. Your product pages, your docs. Rather than naming you from training memory or from a third-party page. That gives you more influence over how you're described, because the source is yours.
One important caveat: read it alongside mention volume. A 100% figure on a brand that's mentioned only a handful of times is far less meaningful than 60% across hundreds of mentions. Small denominators flatter and mislead. Treat it as "share of own-domain citations," not a standalone grade.
Improving it is mostly about being reachable and well-structured enough to get cited in the first place.