As in squash, where you try to return to the T,in volleyball when the ball is passed over the net, you try to get back into your "normal" positions, so when the attack does come, you will be able to move to the appropriate position for that attack (see Receiving an attack).
Below are the normal positions and territories covered by back court players:
The arrows indicate the territories back court players generally cover. Note that the middle player covers the whole of the back line. The back-court setter and outside player's job is to pick up anything front court, e.g. tips and off the block. Anything that goes above their shoulders should be picked up by the back-court middle player.
You will see later, that depending where the attack is coming from, this formation will change, but the back court players' duties will remain roughly the same.