Energy can be transferred in many different ways. For example, if you eat something, the energy from the food transfers to your body allowing you to do certain tasks such as walking or running.
Contributions of scientists led to our understanding of electricity and magnetism is because by using the scientific method, scientists found out important pieces of information they collected, and shared with the world. It helped us understand the things around us even more, if it wasn't for scientists, we would not understand important things such as electricity or magnetism, and the world will be a place of confusion because we wouldn't understand anything.
Sorry the last question is hard-