What is ww2/www2 in the URLs

Question

I have recently noticed some sites with URLs having ww2 or www2. What are they? Is there anything new that came up recently? Is there any link where I can get more information on that?

Answer 1

While www2 may just be a subdomain, it can also be a type of load balancing or mirrors:

http://en.wikipedia.org/wiki/WWW2