The term used to denote the mechanical workings of the organ; in an electro-pneumatic organ such as a cinema organ, is used as a generic term for the mechanism inside the windchests which translates the electrical signal from the relay into the supply of wind to the pipe which makes the pipe speak.
There are many different designs of action. The speed of the action is a significant factor in the responsiveness of the instrument.
See further:
Wurlitzer Pneumatic motors