An HTML sitemap is a regular page on a site, built for people rather than for crawlers, that lists and links to a site's other pages the way a table of contents would. Where an XML sitemap is a machine-readable file submitted to search engines, an HTML sitemap is something a visitor can actually open and click through.
It's most useful on large or complex sites where the main navigation can't reasonably surface everything, giving visitors a single place to see the full structure and find a section that isn't obviously linked from wherever they landed. It doubles as an internal linking asset too: since every page listed on it gets a link from the sitemap page itself, it can help less-linked pages get discovered more easily by both visitors and crawlers. On smaller sites with clear, shallow navigation, an HTML sitemap is often unnecessary; it earns its place mainly once a site has grown complex enough that finding things by browsing alone starts to break down.
