How does energy change form?

Question

How does energy change form?

Answer 1

Usually when you have a junction where energy changes from one kind to another.

For example - when you have an electric motor making something mechanical move.  The energy has changed from electrical current to mechanical motion.

There is usually some energy loss or inefficiency involved in the change (heat in this example, though superconductivity is making incredible breakthroughs).

Answer 2

This question is definitely for an encyclopedia.