It's just a speedy way of getting back on the ground. Instead of recovering straight-in, or joining the circuit from overhead or crosswind, you 'run in' a high speed through initials and then 'break' (climbing turn at high (ish) g to kill the speed) to arrive at a normalish downwind position from whence you can land from a normal finals turn. Used to be seen as the most expeditious and tactically safe way of recovering.