All reverse systems on PWCs are generally refered to as 'gates' but dependant on the model, year and brand will also depend on the type of 'gate' it has..
The bucket:
'Bucket' systems:- Deflect and vector the thrust of water from the jet pump nozzle in several directions when in reverse. The vents on the side are designed to provide maximum turning thrust.
the clam:
'Clam' systems:- when the gate is down, the water is deflected in the same way as the traditional bucket but the gate is attached to the nozzle so that when you steer both the nozzle and gate move.