Sitemap is colloection of pages or xml files that contains for other page links of the website. Usually it tell the user the easist way to navigate all pages, these page may be category wise or having some order for the site sructure.
Generating & providing a sitemap to search engine helps us to knows how to navigate all pages of your site in depths or categories. It also gives info about pages that are rarely apper in navigation.
We can generate a Sitemap by following www.sitemaps.org guideline. There are many online free tools that generate sitemap one of these is Google Sitemap Generator We can generate sitemap quickly by these online tools and submit it to search engine.
Using Google Webmaster Tools submit sitemap : Signup free Google Account then go to Google Webmaster Tools. Login to Webmaster Tools verify the site and submit your sitemap to google. We can also check for sitemap error at Google Webmaster Tools.
Using Bing Webmaster Tools submit sitemap : Signup free Bing Account then go to Bing Webmaster Tools. Verify the site and submit your sitemap to Bing.