There are usually three types of hydraulic system that takes mechanical energy and converts it into fluid energy in the form of oil flow. This mechanical energy is usually taken from what is called the prime mover (a turning drive) like the power take-off or directly from the pickup truck engine.
With each hydraulic pump, the pump will be of the uni-rotational or bi-rotational design. As its name implies, a uni-rotational pump is designed to operate in one path of shaft rotation. On the other hand, a bi-rotational pump has the capacity to operate in either path.