A Hydraulic Power Unit (HPU) is a self-contained system that generates and stores energy in the form of pressurized hydraulic fluid, allowing it to be used for a variety of applications. It typically consists of a pump, reservoir, pressure valve, and a motor. The pump draws fluid from the reservoir and pressurizes it, which is then sent to the pressure valve, where it is regulated and sent to the application. The motor provides the energy to power the pump, allowing the HPU to create and store energy.