"www" is not an alias for a webserver; rather, it identifies a class of servers as being web servers. Unlike "http://" which identifies the protocol and therefore the probable port to be used in the target host, "www" is convenient but not mandatory as part of a world-wide-web address scheme.

http defines the protocol. The default port is 80 but http can work on any port. A common one for 2 web servers on one machine, eg. a chat server I dabbled with a couple of months back is 8080. On my PC at that time, jonbanjo.homedns.org would have reached an Apache web server on port 80 and jonbanjo.homedns.org:8080 would have reached the chat serever. Both servers used http.

www as far as I know is just a name used to find a server within a domain. The Internet works on numbers and DNS has the table to map the names to numbers. eg. Here www.mudcat,org is the machine with the IP address 207.103.108.205 and help.mudcat.org is the machine with the IP address 207.103.108.99

You may notice that help is the same machine as the current backdoor. Names are again used on the virtual servers (one server acting as many servers). 99 is set to default to the backdoor (but it could also be set with the help of dns so that lets say "backdoor.mudcat.org" was another alias. If help.mudcat.org is specified you get the help foum on the same machine. Things don't even have to have the same domain on the same machine. It would be quite possible to have www.jonbanjo.com and www.mudcat.org, etc. all running on the same machine and server each with their own virtual server - that's how shared hosting works.