Running Parallels with Bootcamp

Hey guys. I was really wondering whether i should buy Parallels or just use Bootcamp. I was going to play some games on my new MacBook Air so i just thought of Bootcamp, but somebody told me that you could install Parallels and Bootcamp. I could experience both worlds! Cool!

Anyways, here are my questions. I hope you can answer them!

1. If i read correctly, i heard that you can use Parallels based on your bootcamp partition. Am i correct?

2. Does that mean i only have to install Windows once? And i can only have one part of my hard drive used for Windows, instead of 2 if i use Parallels and Windows separatly?

3. So basically, whenever i use Parallels based on my bootcamp parition, am i using Windows basically on bootcamp at the same time? (please tell me if you want to understand what i'm saying, i might not be clear here)

4. So when i use Parallels do i have all the stuff that i will have on my Bootcamp parition? Like all my files and games and whatnot?

Thanks!