Five main parts of hydraulic system
1 energy device: it supply hydraulic oil to hydraulic system, change mechanical energy to hydraulic energy.
   the most common form is hydraulic pump.

2 implementation device: refers to change hydraulic energy to mechanical energy.  hydraulic cylinder,
   hydraulic motor for rotating movement, which also well known as the implementation compoment of hydraulic system.

3 control and regulating device: it is a device,which control or regulate the system press,flow and flow direction.
   such as relief valve,throttle valve,reversisng valve,open-stop valve.

4 auxiliary device: like tanks,filters,oil tubes.they are essential to ensure the system working normal.

5 transfer medium: hydraulic oil.