What does gearbox mean for airsoft?

It is the "organ" I guess you could call it, that makes the airsoft gun work. Inside, there are many parts:

- Cylinder

- Cylinder head

- Piston (and piston head)

- Spring

- Spring guide

- Tappet plate

- Air nozzle

- 3 gears (sector, spur, and bevel)

- Anti-reversal latch

- Trigger assembly

- Wires to battery

- Wires to motor