Energy is the ability to do work. It is the ability to move an object. Energy can be when a force causes an object to move. There are two types of energy.
Potential energy is the first type of energy. This is the energy of objects that haven't been used yet. Potential energy exists as stored energy before there is any movement. An easy example to understand would be something like a kid attempting to play the violin. The kid may have a lot of potential to become a very good musician. Yet, if they don't put the potential into action by doing things like taking lessons and practicing, that's all it ever will be. Potential. It will never become a reality. Another example would be the mouse trap in this video. Before the mouse trap springs, it has a lot of energy that has not been put into action. (Watch video until 1:22)
Kinetic energy takes place when there is movement. This comes after the potential energy has been put into action. Going back to the kid with the violin, kinetic energy would represent the final product after he decides to take lessons and practice. He will become an excellent violin player. In this video, the marble is placed at the top of the ramp. While placed at the top, it has potential energy. Once it starts moving, it shows kinetic energy because it is moving.
There are several forms that potential and kinetic energy can take. Energy can be stored in matter, produced by the motion of molecules and electrons, and generated by machines.
Chemical energy is potential energy that is stored in matter, such as the energy in food or gasoline.
Heat is kinetic energy that is created by movement of molecules.
Electrical energy is created when electrons move through the matter. Batteries are a perfect example of this.
Sound is energy created by vibrations.
Mechanical energy is the energy of machines. It is created by the moving parts of a machine.
Electromagnetic energy includes things like radios and microwaves.
Nuclear energy is created by the split of a nucleus in an atom.