Whats up with this domain name?

I just came across a domain name that has me a little confused.
I guess its probably a sub-domain, but didn't know you could do this.

The domain is something like

http://www50.domainname com
Would the www50. be a subdomain

Just found it interesting.

Smokey

 

Yes, its a subdomain, you can call a subdomain what you want.

 

Thanks, for some reason I thought there were rules that prevented this.
Cool thanks for the info.

 

You can also create "subdomain.domain.com" and re-direct it to "www.domain.com". I'm still trying to figure out if SE's know the difference, but I doubt the average use would notice. Then again, you can just create a folder and forget subdomains, like "domain.com/subfolder".

 

www. is a subdomain as well but its fixed by the servers.