XML Sitemaps can be used to submit a list of URLs to search engines like Google and Yahoo. The reference website for XML sitemaps is sitemaps.org.
Sitemaps can help search engines to find URLs and this is a great help for sites which do not have very good site navigation, where all URLs cannot be easily found by search engines from the traditional crawling process to collect URLs. Sites where pages cannot be easily found by crawling are for example sites with navigation written by JavaScript, or sites with very many pages dynamically generated and not all included in navigation done with <a>a tags.
This page initially had no links to it, but it is listed in an XML sitemap submitted to Google. and I am using it as a test to see if Googlebot can find it from the XML sitemap alone. Submitting a sitemap to Google is no guarantee for a URL to be indexed. Also URLs with no inbound links from other pages are difficult to be found by search engines, but I think that a URL listed in an XML sitemap can be considered as having a link from the sitemap.
This page has been found by Googlebot from the sitemap alone, cached and indexed in the supplemental index within two weeks of being included in an XML sitemap, it appears at a Google search for "asymptoticdesign stand alone pages" I am trying now to get it out of the supplemental index by linking to it from another page.