Quantum fluctuation

Quantum fluctuation is something that happens when energy changes from one form to another in a small space. For example imagine if you have a toy car and you want to jump over a hill. In order to jump over the hill, the car needs energy. But because the toy car is so small, it can't have a very big engine! So instead the car uses the energy stored in a tiny battery. That tiny battery can't store a lot of energy, so it needs to use the energy it has to jump over the hill. That energy is called quantum fluctuation because it's really tiny and it changes really fast.