A sitemap is a file that contains links to every publically accessible page on a website. Sitemaps are helpful to search engines because they provide a way for search engines to find every page and product on your site. Website owners usually need to create and update sitemap files by hand or use tools to generate them. However, because Shopify is such a great platform, they create and maintain a sitemap automatically for each store they host.
Your sitemap is located at http://yourDomain/sitemap.xml