What is the job of the libero in volleyball?

The libero always wears a different jersey! They are always back row and they always get the deep balls.They have to have a lot of control because they usually hit it when the other team spikes the ball deep (so they have to get it to their setter) and she/he gets it when someone else on their team shanks it. They usually get most of the serves. They have to be a good judge of whether the ball is out or not from the other team.