A sitemap is a list of currently available pages on a website. This information is useful both to users who are trying to find a specific piece of information and to web crawlers which are trying to add pages from the site to the search index. The term instead of site index simply to differentiate it from an A-Z listing that end users would consider an index – a sitemap is more often ordered in some ranking or hierarchy rather than simply A-Z.
The four major search engines support the same format of sitemap. Extensible Markup Language is used to present these to the search engines (XML) and tools such as Google’s Webmaster Tools allow the submission of these sitemaps directly to Google for indexing. Submitting in this way does not guarantee crawling or indexing of all the pages in the sitemap, however for many dynamically generated or content management system hosted sites it is a powerful way to ensure that the search engines have access to information about the entire site.