1. The dry-type prime assisted pump is an end suction pump, which can operate completely dry because the mechanical seal is lubricated in its own independent oil tank. It cannot start by itself, so a compressor is needed to evacuate the air and start the pump through the vacuum generated by the venturi educator.
2. Wet start pump (usually referred to as "self priming") only requires the pump casing to be filled with water before the first start. After that, the liquid will always remain in the pump volute, so the suction hose can dry up without damaging the pump or seals.