Explain the function of Fly wheel?

The main function of Flywheel is to store rotational energy. The amount of energy stored in the Flywheel is directly proportional to the square of its rotational speed. There are some common functions of Flywheel like to provide continuous energy when the energy source is discontinuous and to deliver energy at a faster rate.

For example, a flywheel maintains the constant angular velocity of the crankshaft in a back and forth engine. The flywheel stores the energy when torque is exerted on it by a firing piston, and it releases the stored energy to the crankshaft when a piston compresses fresh air and fuel.