Energy is the capacity or power to do work. Energy cannot be created or destroyed, but can be transferred from one form to another or from one object to another. Energy is categorized into two categories, kinetic energy, potential energy, or both. Kinetic energy is the energy of moving objects. Potential energy that is stored. Thermal and electrical energy are both forms of kinetic energy and elastic, chemical, and gravitational energy are forms of potential energy. Mechanical energy is the only type of energy that is both kinetic and potential. There are many different types of energy and it is used for many different reasons.