The Law of Conservation of Energy is one of the most important Physic's Laws. This law says that energy never is destroyed or created, it just changes from one form of energy to another.
Without going into details of the latest theories on the structure of the Universe and in particular theories about space, time and origin of matter, the principle of conservation of energy is a universal law.
This law says that the energy of the universe remains constant. This means that in any physical or chemical process, the total energy of universe remains constant. If a form of energy increases or decreases is always at the expense of other forms of energy decreases or increases, respectively.
A practical example of this would be the case of a body falling from a height. Suppose we are at a height
What has happened from the point of view of energy?
When the object was at a height
We release the object and this is accelerating as it falls. On reaching the floor height is zero, so that the potential energy is now