Sitemaps are designed to provide search engines like Google, Yahoo! and Bing with a list of a website's pages to include in search results. The Google-developed XML Sitemap is the most commonly recommended sitemap format. An XML Sitemap can be submitted directly to search engines to speed up the indexing of your website and should subsequently be updated and resubmitted regularly.
Benefits of a Sitemap
Website crawling programs, such as spiders and robots, normally discover the pages of your site through inbound links from other sites as well as links from within your site. By providing an XML Sitemap, search engines are provided with a ready-made list of your site's pages, allowing them to spend more time indexing your site rather than searching for it.
Once you have submitted an XML Sitemap, search engines such as Google, Yahoo!, Bing and others will more readily crawl and index your website. Most website owners see a change in page ranking within days!