Usually whatever comes before the domain name ("computerhope.com") is a hostname. So if we have abc.domain.com and xyz.domain.com, ABC and XYZ are supposedly different servers. If you encounter websites with URLs such as
www.example.com and www2.example.com, the domain probably has more than one WWW server, and since you can't have duplicate DNS names, the second server was named www2.
Is this what you wanted to know, or were you inquiring about
Internet2?