A sitemap is a list of all your web site’s pages, that you want to be accessible by the crawlers and the users browsing your web site. Search Engine bots use your sitemap to crawl existing, new or modified pages on your web site. A sitemap is a must for your web site, if you want to improve SEO (search engine optimization) for your site, by making sure that all your pages are acessible and can be found.
Some of the major Search Engines, Google, Bing, Yahoo and Ask, support the Sitemaps protocol. The sitemap is an xml file, that lists all the URLs of your web site, with information like:
– when it was last updated
– how often it changes
– importance of each URL
You can read more about the sitemaps protocol at http://www.sitemaps.org.