Google sitemaps are a service offered by Google as an experiment in web crawling. Google will use sitemaps to inform and direct their crawlers as a way to improve the time to inclusion in their index. By placing a sitemap on your website you're actually directing the crawler as to which pages/urls it should index and add to the search engine's index.
Proper execution of sitemaps is a two phase process, you'll need to create a sitemap in the correct format and upload it to your website. You'll then need keep the sitemap updated each time you modify your site.
You can get more details on google sitemaps and how they are generated, utilized and such directly from Google at: http://www.google.com/webmasters/sitemaps
As google sitemaps are just in their infancy, tools for creation of sitemaps are just now starting to be designed. Our team has identified GSitemap from VIGOS AG as an easy to use client side application for generation of sitemaps. This tool can be found at Vigo's homepage
Another option is GSiteCrawler from SOFTPlus, available at: http://johannesmueller.com/gs/
Applied Innovations currently does not support execution of the Python based application provided by Google directly on our shared servers and requests that clients please utilize one of these alternative tools.