Small pully behaind the ac is the belt tensioner for the ac belt. The ac, alternator, and power steering all have their own belts that run them. The other belt there is your timing belt which powers the cams and water pump, and goes to it's own tensioner too. You take the ac belt off/out your ac won't work. Thats all that will happen.
To take that belt off, remove the ps pump (just push it to the side, don't have to undo any hoses) and there's a ten mm bolt right behind ac pump that tightens/loosens the tensioner. Loosen it till you can slip the belt off the pump. Can't remember if the ac belt is behind or in front of the other belts in the crank. You might have to take one, or both the other belts off. Txt me if you get stuck, or bring it up here one of these days and I can help you. Shouldn't take long at all.