Energy is the main cause of anything. Cars, lights, music, computers, etc. Most of us know energy as electricity or electrical flow. But energy is actually the thing that creates electricity and then it is converted to electricity. Energy sources come in two types, renewable, and non renewable. Renewable sources are sources that couldn't end but couldn't be relied on as they don't produce energy as much as the non renewable sources, for example tidal energy. The waves won't run out, but we don't know how often we could find them. While the non renewable sources couldn't be used for ever, they would eventually run out, such as fossil fuels. But they produce a lot. Without energy think of our lives as lame as they would be two hundred years ago.
There are nine forms of energy, elastic (potential), gravitational (potential), thermal, kinetic, chemical, sound, heat, electrical and nuclear. Energy could be changed from, elastic to kinetic. For example a bow and an arrow. When you pull on the bow, you are storing elastic energy. When you release, the arrow and the string its self change to kinetic and move forward. From gravitational to kinetic. Fro example a parachute, when the parson jumps from a plane, he starts loosing his gravitational energy and gains kinetic energy. From kinetic to gravitational. For example, a boy on a swing, when he starts, he moves forward gaining gravitational potential energy, as he falls back, he is changing the gravitational to kinetic. From electrical to sound. For example, a jukebox, you plug it into the electricity so you could play your record and changes that energy to sound. From c chemical to heat and light. Example, a match, when you rub it on the side of the box, you are loosing chemical and gaining heat and light. From electrical to heat and light. For example you desk lamp changes the electrical energy you give it to heat and light. You could also change chemical energy to kinetic in a car.