This is very basic physics theory. Energy is never created nor destroyed.
This can be counter intuitive if you are studying nuclear physics since Einstein told us E=mc^2. Energy coming from just mass? This is the reason why the (really small) percentage of the universe we know, which isn't dark matter or dark energy, is generally called energy and matter.
According to the law of conservation of energy, energy can neither be created nor it can be destroyed. It can only be transformed from one form to another.
For example, a ball at rest will have potential energy but the moment this ball comes into motion then its potential energy will convert into kinetic energy.
Thus, we can conclude that following two statements are true about energy transformations.
