We know world wide web, the internet web, simply www, and we are very femilier with www.hostname.com

somebody always need a www before any host name to indicate , he is using an url :)

Agree, but now a days i have been hearing that www1 or www2

eg: www1.freewebs.com/sajithmr

what is the difference between www and www1.

Dont worry , they are merely sub domains like, mail.google.com or course.sajithmr.com . Nothing more .

But some organization uses these “special subdomains” differnet purpose such as load balancing, or categorization or role based routing.

Load Balancing means , the initial request to www server may redirect to less busy server such as www1 or www2.

Somebody fears about the serach engine’s apporch on this subdomains. Since www1 and www2 provides same content in some case, and since search engine considers www1 and www2 as two different domains,
content duplication (a violation to search engines rule ) may be reported. If www1 and www2 have a perment redirection (301) i think (Only i think) the duplication may not be a problem.

And lets come into the latter one. Role based routings.

For example http://www.potsdam.edu is the main site of postdam university. But they are using http://www2.potsdam.edu for their students contribution with descriptions and implementation notes etc

Here these two subdomains (www and www2) are using for different role implementation

Please comment this article if you know more about this www subdomains

Refer this blog : http://blogsandbucks.com/what-is-www2-or-www1/

Thanks and Regards
Sajith M.R