I used to work in a department store that had these. It means that cash is not carried around, it is just put into the pod and the pod gets sucked up and deposited into the secure room where the safe is. There was points along the pipe that increase the pressure (i think), to keep the pod moving.

I was working under one of these points with a collegue one day when we heard a farking horrible noise from above us, then a fine yellow powder along with small pieces of yellow plastic fell out of the vent close to us. It all used to be a wad of $50 notes that was being cleared from a register. (Australian $50 notes are yellow). un-farking-lucky to you target (said department store).