What is sitemap navigation?
In short, a sitemap is an outline of all the pages/links on your site which will help inform how you structure your navigation. Whereas navigation is the series of menus users will take to browse through your site and its content.
What is high-level sitemap?
Sitemaps can be represented in a coarse-grained or a fine-grained way. On the one hand, high-level sitemaps (also called blueprints) show how the main sections of a web site fit together. They do not show all pages. On the other hand, detailed sitemaps document the site finer-grained.