Glossary
Sitemap (sitemap.xml)
A sitemap is an XML file listing every important URL on a website, used by search engines to discover and prioritize content for crawling.
A sitemap (typically /sitemap.xml) lists every URL a search engine should know about, along with optional metadata: lastmod (when the URL last changed), changefreq, and priority.
Sitemaps are especially important for new sites with little inbound linking and for large sites with deep navigation. They're how Google finds URLs that aren't linked from anywhere obvious.
Submit your sitemap in Google Search Console and Bing Webmaster Tools. For sites with more than 50,000 URLs, split into multiple sitemaps and reference them from a sitemap index.
Example
A new site with 30 pages and zero inbound links can get every page indexed within 48 hours by submitting a sitemap to Google Search Console.