ww2 are subdomains. They have no special meaning to a browser, other than the fact that they are part of a larger domain. These days, the above subdomains are used mostly on the basis of tradition. Quoting this question on StackOverflow:
People running large(-ish) sites used to do this when they needed to
break up the load between more than one server. One machine would be
called www then the next one would be called www2, etc.
Today, much better load balancing solutions are available that don't
require you to expose your internal machine naming conventions to the