Suspension 101
There are two forms of suspensions for armored fighting vehicles: tracked and wheeled. For tracked systems the vehicle rests on a continuous, flexible track. Road wheels are those wheels that sit on that part of the track that rests on the ground. Return rollers, guide or top rollers may support the top portion of the track. The drive sprocket is a toothed wheel that transfers drive power from the engine to the track. The idler wheel, normally smooth and located at the other end of the vehicle than the drive sprocket, is a freely turning wheel that provides support to the other end of the track.
The following picture of the German Gepard shows the suspension of a tracked vehicle.