Air pump is a device used to push air. Examples include bicycle pump, which is used to inflate an aquarium or a pond with air stone; gas compressor used to drive pneumatic tools, air horn or organ; air box used to aid fire; vacuum cleaner and vacuum pump.

Pumps and compressors use very similar mechanisms, and basically perform the same action, but the fluid state is different. In some cases, there is a terminological intersection, but here are some stereotypes:

• the compressor operates on a compressible fluid (usually gas). The pump operates on approximately incompressible fluid (usually liquid).

• the compressor is designed to produce a high pressure rise on a closed system; the pump is designed to produce a relatively small pressure on a free flowing system with a minimum back pressure.

The pump is usually used for continuous flow operation, and many low-end compressors must have intermittent duty cycle.

• the compressor normally turns off the feedback sensor when the required pressure is reached. The pump has a fixed design and can operate freely on its performance curve when conditions change