The law of conservation of energy states that energy cannot be created or destroyed, only converted (transformed) into other forms of energy. In a closed system (where nothing escapes or is added) the amount of energy present at the beginning of a process is the same as the amount of energy at the end.
When energy is converted from one form to another it is known as energy conversion.
This is most easily seen and calculated with mechanical energy, the sum of the potential and kinetic energy. When an object releases its potential energy, it is transformed into kinetic energy. The loss of one is the gain of the other.
