A subdomain is a second website, with its own unique content, but
there is no new domain name. Instead, you use an existing domain name
and change the www to another name. The subdomain name looks like
forums.domain.com, help.domain.com, help2.domain.com (assuming you
already host domain.com).
To learn how to setup a subdomain, watch this movie tutorial.
To create a subdomain, please do the following: