Gravitational energy
An object gets gravitational potential energy when it moves uphill. The energy used up when moving up the hill is changed into gravitational potential energy. When the object comes back down again, the gravitational potential energy is turned back into kinetic energy (movement). That is why riding a bike up a steep hill is very hard, but when you are coming back down, you will not need to pedal at all - you are being powered by the gravitational potential energy that you stored when you rode up the hill. Another way gravitational potential energy helps us is by keeping earth and the other planets in orbit in our solar system around the Sun.