A site map (or sitemap) is a web page that lists the pages on a web site site, typically organized in hierarchical fashion. This helps visitors, and search engine robots, to find pages on the site.
Site maps can improve search engine optimization of a site by making sure that all the pages can be found. This is especially important if a site uses Macromedia Flash or JavaScript menus that do not include HTML links.
Site maps do have limitations. Most search engines will only follow a finite number of links from a page, so if a site is very large, additional strategies besides the site map may be required that search engines, and visitors, can access all content on the site.
Google maintains a feature called Google Sitemaps that allows web developers to publish lists of links from across their sites. The basic premise is that some sites have a large number of pages that are only available through the use of forms and user entries. The sitemap files can then be used to indicate to a web crawler how such pages can be found.