Dual Monitor Advantage

Okay, I'm a noob about this "dual monitor" thing, can anyone tell me the main advantage of it?

I'm thinking that, is it possible to use one monitor to watch anime (full screen) while I use the other monitor to surf net, chat, watever, etc.? 

>>18
Not 14, but yes, any device driver theat isn't from Microsoft (if you're running Windows, obviously) IS third party.  WTF is your problem?