Summary: So, this one time, like 13 or 14 billion years ago, there was this big bang. This energy is the basis for all the energy used today.
More recently, humans have relied on a number of energy sources. The first being plant matter, the next being animals, which get their energy from plant matter. Next came biomass, whether wood, dung, other plant fibers. Eventually, we figured out we could use animals, the wind, and the sun to do work. Then came fossil fuels that we could burn and nuclear reactions we could harness. Now, with all of these options, it is time to reassess where our energy comes from.