WHEN A FORCE IS APPLIED TO AN OBJECT AND CAUSES OR RESISTS ITS DISPLACEMENT, IT CHANGES THAT OBJECT'S ENERGY.

The product of a force and the displacement it causes is called work. In a sense, the work done on an object gets stored in the object in some way: in its overall motion, in the motion of its particles, or in its position away from an object that is pulling it to itself. This stored work is called energy. This energy can be used at another time to do work again.