Nadini and everyone, just wanted to clarify that Site Map is not only the XML we use to submit to Google.
Site Map is a overall picture of how the site has been laid out.. what sections, sub-sections and pages for someone to get a bird's eye-view. Many of the top Corporate / User help websites in the world have a site map section. Here is an example of Site map on Infosys website.
The XML (eXtensible Markup Language) coded Site Map is a file that lists down all pages on the site, including sections and feeds to the Google Bot. This makes life easy for Google Bot and other similar robots/crawlers by telling them that you have X number of posts, and where they are. The Robots/Crawler then crawls to each of these pages and saves relevant information to their servers to help search functions.
Your XML Sitemaps contiain following information:
- URL - the address of the page
- Priority - You can give priority to some of the pages/pages - Google / other bots identify this information and you have considered information on a particular page on higher priority. Prioirty is given in %. 100% means full priority and 0% none.
- Change Frequency - How often will this page change. You Blog home page will have a change frequency of Daily, but others can be set at monthly. This way, Bots will not hit your servers daily, except for the home page where you will change content more freqently.
- Last changed date - the time stamp when you last changed your content
It is always advisable to have your Sitemap updated to the T. If you do not have a site map updated to the latest changes, chances are that the Robots/Crawler may ignore the new pages.
On self-hosted wordpress, you get plugins that can do this for you, and generate a site map daily.
Read more on http://sitemaps.org/