A WIREFRAME is an outline of a website. It is the first step of the creation of a site. Good web designers start out with a wireframe sketch in order to visualize their ideas on paper.
Tips for drawing wireframes:
A SITEMAP is a visual map of the navigation of a website. The more pages your site has, the more complicated your site map will be. A sitemap for Apple will be GIANT, but a sitemap for my site will be rather small. Most large sites have the sitemap accessible as a page so that users don't have to navigate throughout a large site.
Visit the Apple sitemap page for an example.