Energy is the ability to do work and comes in 2 basic forms: potential energy and kinetic energy.
Potential Energy
Potential energy is stored energy - you may think about how a battery stores energy to be used later. In the human body, a common form of potential energy is the energy stored in chemical bonds. That's right the covalent bonds you learned about earlier store energy that can be released when the bond is broken! Another way the body stores energy is with concentration gradients across cell membranes (more on this later).
Kinetic Energy
Kinetic energy is the energy in motion and comes in many forms: radiant (heat), sound, mechanical, and electromagnetic (light).