A sitemap is a simple page on your website that shows the whole structure of your website. HTML site map is more user-oriented i.e. it is for the users to see the whole structure of your site so that they can navigate through the site easily. An XML sitemap is for Google which makes it easier for Google to index your whole site. You can submit your xml sitemap using the google's webmaster tools (www.google.com/webmasters/tools/)