How do I create a Google Sitemaps file?
Search engines need to "crawl" or "index" your site to take a snapshot of the pages that appear in the search engine.
Some search engines (most prominently Google) can use a "sitemap" file to decide how to crawl the site in a more intelligent manner (for example, by crawling frequently changed pages more often). The site www.sitemaps.org has more details about sitemap files.
If you want to create your own sitemap file, you can generate one at http://www.xml-sitemaps.com/ if you enter just a few details about your site.