Push, pull and hydraulic are different types of clutch slave cylinder kits. The specific type of kit required depends on the type of master clutch cylinder being used and the type of clutch system. Clutches can be mechanical or hydraulic.
Mechanical clutches are typically either a push or pull configuration in which a clutch fork and pressure plate are used to transfer the force that is being applied to the clutch pedal. This force that is transferred is used to either push or pull the transmission into the neutral position so that the gears may be shifted. Hydraulic systems use a fluid actuator to transfer the force from the clutch pedal to complete the process.