A page consisting of links to all the pages of a web site. For a small site, your site map can have direct links to every page on your site. On the other hand, if your site consists of hundreds of pages organised in directories, the site map of might run into 2 or more pages. As the term suggests a site map is a map of the web site and can be a list of links or a more complex representation. Search engine crawlers, spiders or robots increasingly rely on a sitemap to find all of a websites pages and products.
Google has implemented the free Google sitemap service for web sites to submit maps of their entire sites. The sitemap guarantees that all of your pages will be considered for inclusion in Google's index.