Potential energy is energy stored inside an object. An example of potential energy is a loaf of bread because the energy in the bread isn't moving inside it. Kinetic energy is moving energy. An example of kinetic energy is a running person because it is using energy that is moving while he is running.
Energy has many forms. Some forms of energy are mechanical, heat, sound and chemical energy.
Energy cannot be created or destroyed, but it can be converted from one form to another form. For example, in a laptop electric energy from the plug converts into sound and light energy when the laptop turns on.
In order to understand ourselves better, we need to understand what our body is made of, which is energy. With the knowledge of understanding energy we could invent new things because everything is made of energy. We could predict what is going to happen with the earth. These things couldn't be done without understanding energy.