Automatic swimming pool cleaners come in three basic categories:
Automatic pool vacuums-these automatic swimming pool cleaners work off the suction of your swimming pool pump through a vacuum hose.
Pressure operated automatic swimming pool cleaners-these operate off the pressure or return side of your equipment plumbing,either directly or by their own pump via a dedicated plumbing line.
Robotic self contained units-these units,usually with a tank-like tread,are powered by their own extension cord or a rechargeable battery. They have their own filtering system and run either by a computer controlled program or a remote control.
At the bottom of this page,there is a link for troubleshooting these systems.