Basic Terminology On Potential Energy
We can simply define potential energy as stored energy. To understand better this form of energy, we'll take an example. Let's consider that we have a book on a table.
The gravitation will pull the book down, so we can say that it has gravitational potential energy. This energy would be smaller if the book would be placed on the floor, because the gravitational force would be smaller. The presence of the potential energy in this case, could be demonstrated by sliding the book off the table. The book will clearly fall on the floor, and due to its motion it will gain kinetic energy. After that, kinetic energy will be converted into heat (because of its motion) and sound (due to the impact with the floor). Among the factors that influence the gravitational potential energy created we find the mass of the object, the gravitational field strength and of course, the distance that the object is lifted. For example, because of the Moon's reduced gravitational force, it would be easier to lift the book there.
To give another example, we'll take the example of the two lakes found in Dinorwig, Wales. A particularity of these two lakes is that one of them in higher than the other. Whenever an energy surplus is not needed, water is pumped to the higher lake. And when more energy is needed, the water flows back through some turbines, generating electricity. By doing this they reduce the costs, but some of the original energy is wasted through the friction process. In this case, by doing work against the natural process of gravitation, potential energy is stored.
But gravitational potential energy is not the only form of potential energy. The other forms are elastic potential energy, electric potential energy, rest mass energy and because of the bonds between atoms and molecules, we can also include here chemical energy. The most important form is the electrical potential energy. This is defined as the work that must be done to move an electrically charged object from a certain distance away to its present location.
To summarize it all, I can say that potential energy is the energy which an object has stored due to its position relative to some zero position. Every object contains gravitational potential energy if it is positioned above his zero position. Just lift an object from the ground, and you will obtain potential energy.