Search Engines use your Sitemap to learn about the structure of your site and to increase the coverage of your web pages. A well-designed sitemap allows for search engines to easily locate and index all relevant pages of a website.
Sitemaps should be easy to find for a search engine, ideally be placed at the root level directory as this gives the page better visibility. Links to the sitemap page should ideally be provided from all web pages in a website.
Creating and submitting a Sitemap helps make sure Google and the other search engines know about all the pages on your website.