Definition
Plain language
A file on a website that lists its pages, meant to help search engines and automated tools find everything.
As stated in the literature
A structured (usually XML) listing of a site's URLs published at a known location for crawlers; agents probe it, alongside robots.txt, to enumerate a site's pages when direct navigation fails.
Why it matters: It gives crawlers and agents a reliable way to find all of a site's pages when ordinary navigation comes up short.
For example, an automated tool reads a site's sitemap file to discover every product page even when there's no menu link pointing to them.
Heard on the show
“It scrapes the site's robots file and sitemap.”Episode 061 — When Helpful Agents Go Sideways: A 404 Error, Campus Security, and Why Alignment Misses This