Your account allows to host several domains. The number is depending on the hosting plan you choose.
In Virtualmin, your main account is yoour domains, and all accounts below it are names subdomains. It migth be confusing as it has nothing to see with DNS.
As an example, if the dns name linked to your main account is aaa.com, it is absolutely possible to have a subdomains (in Virtualmin definition) with the dns name bbb.com.
