An XML Sitemap is a file that helps search engines like Google understand the structure of a website. It lists all the important pages, making it easier for search engines to find and index them. This is especially useful for larger sites with many pages or for new sites that may not have many external links yet. By providing a clear roadmap of a website's content, an XML Sitemap can improve a site's visibility in search results. Webmasters can create and submit this file through tools like Google Search Console to ensure that their site is properly indexed and ranked.