Potential energy is the amount of energy that is stored within an object relating to position. As an example we can use a bow and arrow. A bow has no potential energy when it is just laying there but when a person pulls back on the bow it now has potential energy. Two kinds of potential energy are gravitational potential energy and elastic potential energy. Gravitational potential energy is the energy stored in an object based on the objects height. Elastic potential energy is the energy stored in an object because of compressing or stretching of the object.
Potential difference is the difference in potential energy between the final and beginning location of the object. This has caused a change in the potential energy.