A .xml sitemap is simply a list of URLs that is designed for spiders to identify all pages attributed to the particular website. The sitemap generally facilitates the search engine bots to locate URLs in order to index them within their search results. However, it is known that Google does prefer to locate the URL’s independently of the sitemap to improve the knowledge of that page in terms of relevancy, and link power.
These .xml sitemaps are the modernised version, moving forward from the traditional html sitemap. The new .xml sitemap protocol was introduced by Google as companies were adding more content and complexity to their sites, so a one-design protocol has made the crawling process easier to handle and understand.
Below you can find a small sub-section of the Bough SEO sitemap, which provides an idea of what a .xml sitemap looks like visually: