Potential energy is energy stored internally in an object.
A typical example is the energy stored in a compressed spring, or the energy something has by virtue of being lifted a certain height above the ground. For gravitational potential energy, the force is the weight of the object, and the distance is the difference between its starting height and the height to which it is raised. Kinetic energy is the energy a moving object has by virtue of its movement, and is equal to half the mass of the object times the square of its velocity. Thus if a ball is lifted to a certain height, it gains potential energy. If it is then dropped, the potential energy is converted into kinetic energy as it looses height but gains speed.