Reinventing the wheel

"Reinventing the wheel" means doing something that has already been done before, instead of using the original idea or doing it in a better way. Imagine you have a toy car that has four wheels, and you want to make a new toy car with four wheels too, but you don't look at how other people have done it before. That means you're "reinventing the wheel" because you're making something that's already been made, but you're not using the knowledge that other people have already discovered. It's important to learn from others' experiences and knowledge so that you can make your new thing better and different from what already exists.