We can use it in countless ways. But we don't know anymore about what it ultimately really is, or where it came from, than we did 5,000 years ago. All we really have learned to do is use mathmatical formulas to describe its behaviour. The ultimate nature and origin of energy , at least so far, is for theologians and philosophers to explore and debate. Scientists and engineers just learn how it behaves and use that knowledge.
Scientists use the knowledge to study and explain our world and the universe.
Engineers use the knowledge of how energy behaves to make the machines and devices that make up our modern technological world. If you like mysteries, you'll love energy . So we'll call it the Mysterious Everything . If you don't like change, this stuff might make you uneasy. Because energy is always changing.