The wheel is like a lot of levers that rotate in 360 degrees where the fulcrum was is now axle.The axle is in the middle of the wheel.
The wheel rotates around the axle. The wheel is best as a cylinder because the cylider is an shape that rolls .This cirlular moves shape easier a cross any surface . The wheels go on the machine to make it easier to move.
Some examples of wheels are on a car,a steering wheel and most moving machines.