A valve is a device that regulates, directs or controls the flow of a fluid, gases, fluidized solids or slurries, by opening, closing or partially obstructing various passageways. Valves are technically fittings but are usually discussed as a seperate category.

For operation of valves, actuators are being used to minimise the human errors during operation or to control the system very pricisely.

An actuator is a component of a machine that is responsible for moving or controlling a mechanism or system, for example by actuating (Opening or Closing) a valve or damper; in simple terms it is a mover.

The actuator may be electric, pneumatic or hydraulic

An actuator requires a control signal, which is relatively a low energy and may be electric voltage or current, pneumatic or hydraulic pressure, or even human power.