domain types?, I need help understanding this? Options

[Maccabee]

Ok I need some help understanding this?

Ok here is my hosts features page:

http://www.hostmonster.com/hosting-features.htm

As you can see they have unlimited domains, add-on domains etc and I need to know what that means?

Does having unlimited add on domains mean If my domain is example.com I can add another domain like sample.com for free?

Or does that mean if I had sample.com registered like at 1and1.com I could put it with my hosting account and share the disk space and bandwidth with example.com for free?

I really need help with this?!

And if you only want to answer the first part thats fine but could somone give a link that explains what a:

add-on domain

parked domain

sub domain

and what it means to have unlimited domain mean?

Thanks!