Sitemap is a file containing a list of the web pages on your site, particularly the links that might not otherwise be discovered by search engines during the normal crawling process. Using a sitemap to give search engines information about your site will typically result in faster and more complete indexing of your web pages.
You’ll need to submit your sitemap to the search engines. To submit your sitemap to Google, sign up for a Google Webmaster Tools account and follow the instructions here. For instructions about other search engines, look through online resources.