Motion can simply be defined as the change in position of a body while energy is the ability or capacity to work.
Mechanical energy is one of the forms of energy and is subdivided into potential energy and kinetic energy. These energies are energies that determine whether a body or an object is moving or not.
When a body is in a position, the energy possessed by such body by virtue of its position is known as potential energy while when a body is moving (in motion), the energy possesses by this body by virtue of its motion is the kinetic energy.
For instance, a ball rolling down an inclined plane is initially at rest at the top of the incline showing that the body has maximum potential energy and zero kinetic energy (since the body is in a position at this point).
As the ball rolls down the incline, it gains momentum and its kinetic energy keeps increasing along the plane while the potential energy keeps decreasing. Once the body gets to the bottom of the plane, the kinetic energy becomes zero while the potential energy is at maximum (because the body is at rest at this point as well).
