You can find basic hydraulics schematics on Capetronics.com, CrossMfg.com, MachineryLubrication.com and Science.HowStuffWorks.com. The websites illustrate a basic hydraulic system consisting of a reservoir, a pump, valves, fluid and a motor.
In a hydraulic system, force exerted at one end moves through a confined fluid to another end. The system is an application of Pascal’s Law, which states that pressure applied at any point upon an enclosed liquid is transmitted undiminished in all directions. Since the liquid is incompressible, it enables the use of little effort to generate multiplied forces. The fluid also provides lubrication.
The reservoir holds the fluid and allows impurities to sediment, and its walls cool off the fluid by releasing heat. Air escapes because of the reduced pressure in the reservoir.
The pump displaces the fluid from the reservoir to the hydraulic system, increasing the pressure of the liquid and raising its energy. The pump has to face resistance for this to work.
A hydraulic system has directional control and pressure relief valves. Directional control valves direct fluid flow in the hydraulic system. Pressure relief valves open when the pressure exceeds the set value; they prevent pressure buildup.
A hydraulic actuator, such as a motor, is where the hydraulic energy converts back to mechanical energy. It is possible to multiply or divide the energy produced by varying the size of the pump and the reservoir.