Potential energy is the stored energy of position or its chemistry. Potential energy can be changed to kinetic energy. Kinetic energy is the energy in moving things. A wind-up toy sitting on a table has potential energy. You wind it up and let go and it moves. The potential energy changed to kinetic energy. Substances like wood, coal, oil, natural gas, and gasoline have stored energy because of their chemistry. They can burn. When they burn, they give off heat and light energy. Potential energy can change to kinetic energy either slowly or very quickly. All energy starts out as potential energy.