There are 3 different types of pool cleaner in the market: suction, pressure and robotic
Pressure side cleaners use the pressure of the water as it gets returned back into the pool to propel itself around the pool’s bottom and walls vacuuming up all dirt and debris. The debris goes into a bag attached to the side of the cleaner. The debris bag catches all the debris and prevents it from going into the filtration system and pool filter – unlike a suction cleaner. This reduces wear and tear on the pump and pool filter .
Suction cleaners Unlike pressure side cleaners which need a separate pump to operate, they are able utilize the pool’s filtration system to move around the pool’s bottom and walls, vacuuming dirt and debris along the way. The automatic pool cleaner attaches to the suction side of the pool’s plumbing, either at the skimmer, or on a separate side port specifically designated for the cleaner (a feature usually on newer pools). The dirt goes through the hose and into the pool’s pump strainer basket, leaf canister and/or pool filter. Suction side cleaners work best in areas where dust and small debris (ie: leaves and flowers) can get in the pool.
Robotic Cleaners are powered by low-voltage electricity, rather than your pool pump or a booster pump. Since your pump runs less, your energy costs are reduced. Plus, their built-in filter further reduces use of your pool's primary filtration system lowering energy costs even more, extending the life of both your pump and filter, and increasing the amount of time between filter cleanings.