Nuclear power is a way to make electricity. It works by splitting apart atoms of uranium in a special kind of machine called a nuclear reactor. This process makes a lot of heat which is used to boil water and make steam, which can turn a turbine to make electricity.
The controversy about nuclear power is because, when uranium is split, it makes a lot of dangerous waste. This waste is radioactive, which means it can make people sick if they get too close, and it takes a really long time to stop being dangerous. So, people are worried about what to do with the waste and what would happen if something went wrong at the nuclear power plants. There have also been accidents in the past where nuclear power plants have released a lot of dangerous radiation.