Pneumatics is a branch of engineering that uses gas or pressurized air. A pneumatic system is powered by compressed air or inert (non-reactive) gases. A centrally located compressor powers special pneumatic devices.

This chart is a direct comparison between pneumatics, hydraulics and electric-powered machinery: 

Characteristics Pneumatic Hydraulic Electric
Complexity Simple Medium Medium/High
Peak power High Very high High
Size Low size/force Very low size/force Medium size/force
Control Simple valves Simple valves Electronic controller
Position accuracy Good Good Better
Speed Fast Slow Fast
Purchase cost Low High High
Operating cost Medium High Low
Maintenance cost Low High Low
Utilities Compressor/power/pipes Pump/power/pipes Power only
Efficiency Low Low High
Reliability Excellent Good Good
Maintenance Low Medium Medium