What does pneumatic mean?

Pneumatics is a section of technology that deals with the study and application of pressurized gas to produce mechanical motion.

So, imagine, a hydraulic system that uses gas instead of fluid to obtain the same result.

I was fortunate enough to consult Michael, the engineer of the production department of A&S Hydraulics Co., Ltd.. He explained to me that hydraulic pressure is based on liquid as the working medium and uses the pressure energy of the liquid to transmit power. Pneumatic is the use of compressed air as the power source to drive the machine to complete the telescopic or rotating action.
The hydraulic system consists of five parts, namely the energy device, the actuator, the control regulator, the auxiliary device, and the liquid medium. The hydraulic pressure is widely used in industrial and civil industries due to its large transmission power, easy transmission and configuration. The actuators of the hydraulic system (cylinders and hydraulic motors) are used to convert the pressure energy of the liquid into mechanical energy to achieve the desired linear reciprocating or swiveling motion. The function of the energy system (hydraulic pump) of the hydraulic system is to convert the mechanical energy of the prime mover into the pressure energy of the liquid.
Pneumatic is characterized by the compressibility of air. When the air is compressed and stored, the air has the elasticity like a spring, and then the control element controls its direction to drive the rotation and expansion of the actuator. How much air is inhaled from the atmosphere will be discharged into the atmosphere, without any chemical reaction, and will not consume any components that pollute the air. In addition, the viscosity of the gas is smaller than that of the liquid, so the flow rate is fast and environmentally friendly.