I have no clue about subdomains so this is a simple question.

I have a site hosted on a subdomain and when I post at the domain's forum, if I reach a certain amount of posts, I get rewarded with things, one of those includes my own sub domain.

So I have one site already but this summer I plan to make another site, so can I use the subdomain to create another site on my own subdomain?

In other words, I have an anime site, and I'm planning to build a Legend of Zelda site, so if I use my subdomain, will it mean the Zelda site will have the same name somewhere within the url as my anime site?

I think the urls would be something like:

firstsub.maindomain.com
and
secondsub.maindomain.com