Potential energy, or strored energy, is the thing that makes energy inside of objects. If rock has fallen down then it has built up potential energy in it; there are many types of potential energy. The first one is "Gravitational Potential Energy" is energy that makes the rock go down and depends on the object's mass. The second type of Potential energy is "Elastic Potential Energy." It is the energy stored when an object is stretched or sueezed. The last type is "Chemical Potential Energy." It is when you eat, this type of energy is stored in bonds between the atoms that move up matter.