To understand how things work sometimes you have to take them apart and look inside. We can't really look inside of a star but we can try to imagine what it might be like. Let's start with looking for the source of a star's power.
A lot of things in your house need power to run. Your remote control cars need batteries. Your radio needs to be plugged into the wall because it runs on electricity. Stars are very different from anything you've seen on Earth. Stars work by changing matter into energy. That's right ... the stuff that makes up all of the things on Earth is changed into energy (heat and light) inside of a star!
It just takes a little matter to make a whole lot of energy. Look at the jellybean in the picture. If all the matter in that jellybean were changed into energy there would be a very big explosion -- big enough to blow up a small island.