Pneumatics utilizes the same theories that hydraulics do, but instead of using oil, it uses compressed air to propel its movements. As of late pnematics has been an increasingly popular in implementation with various eastern european forms of bondage - ask your nearest kinky (sexually starved) engineering student about it.
Person (who finds great delight in pointing out the rather obvious) A: Woah! Check out that super-awesome brakes on that truck/train!
Person (who recites basic knowledge available to the general public through the uses of Wikipedia) B: Oh yea - that's an example of pneumatics at work.