Energy is the ability to do work. It is a scalar quantity and is always measured in Joules.
There are different forms of energy and these include:
Chemical Energy: Energy stored in the chemicals which is used as food or as chemicals in giving light energy. It is also easily converted to heat.
Mechanical Energy: Energy due to motion or rest. Position of a body.
Nuclear Energy: Energy stored in the nucleus of atoms which can be used to generate heat.
Sound Energy: Energy produced by the vibration of air particles
Hydro Energy: Energy produced from water at a particular height.
Solar Energy: Energy produced from the sun.