XML Sitemap
An XML sitemap is a machine-readable list of all the relevant URLs on a website that serves search engines as a signpost, helping them find and crawl pages reliably – particularly useful on large websites or ones with weak internal linking.
In practice
The sitemap should contain only indexable, current URLs and should be referenced in robots.txt and in Google Search Console. It is no substitute for good internal linking, but it complements it usefully as an additional crawling signal.