They usually have an oval or rectangular platform, a motorized fan and a large skirt material to trap the air underneath the vehicle. This air cushion underneath the hovercraft is called the plenum chamber . This plenum chamber is formed by the bottom of the craft and the skirt material. The air flowing into the plenum chamber will form a ring of air circulating around the base of the skirt to insulate the air cushion from the lower pressure air outside the skirt. This ring of air keeps the air under the craft from escaping.
Most large hovercraft have a large propeller attached to the back of it to propel it forward.
Rudders attached to the propeller's housing allows drivers to steer the vehicle. On some smaller hovercraft, steering is performed by the driver leaning left or right. Steering a hovercraft is a little tricky. There's no contact with the ground, so steering the craft will feel slippery. In order to stop the vehicle, you just have to slow down the engine and the craft comes to a rest on the ground.