Basically, there are two types of sitemap, which widely used -
XML Sitemap - XML Sitemap like a blueprint for your house and each web page were a room.
XML Sitemaps are important for SEO because they make it easier for Google to find your site’s pages—this is important because Google ranks web PAGES not just websites.
HTML sitemaps - HTML sitemaps help a visitor to easily find the web pages in your website. It includes each and every page of your website. You can create it in HTML language or made it done with your developer. And remember to make sure that it contains all your main web pages/categories with about us contact us pages as well for an example.