An XML sitemap, or Extensible Markup Language, is a file on your website that helps search engines find, crawl, and index pages.
They let you include extra information about each page. For example, the date the page was last updated. It helps search engines understand your site’s content and how often you update it. Though XML sitemaps are not required, they can help improve your site’s visibility in search results (SERPs).
If you are using a WordPress site, you should use the YoastSEO plugin. It automatically creates and updates your XML sitemaps.