Whats going on with the Spider-man movie series?

I've been watching videos on spider-man 4 with toby maguire that they are shooting right now and the amazing spider man movie with andrew garfield that i guess is already done shooting. i read that spider man 4 might come out in 2011 and the amazing spider man is going to come out 2012. But im confused because why is andrew garfield playing peter parker and what is the amazing spider man movie all about? is that going to be spider man 5 or something?