Question re: the Buffy Vamps

What exactly is the mythos surrounding the vampires in the Buffy universe? From what I've seen so far of the series, there seems to be mention that there's actually a demon that possesses a person when they get turned? Is that right? If so, do we learn more about how that "works"? Like, is it a Goa'uld type thing where they become trapped in their own body? Or do they die and then the demon inhabits the corpse? I'm just a little confused as to how it all works...

Wow! Re: JumpCon

It looks like JumpCon is basically closing its doors. The Boston event was just canceled and from the looks of the message on their front page, it looks like nothing else is gonna happen either...

Oh! And I finally got through to Dr. Horrible. Awesome. Awesome awesome awesome! This would be the coolest TV show ever! LOL