Nuclear energy can be used to create electricity.
During nuclear fission the nucleus, (of an atom) breaks apart into two nuclei. During this process a large amount of energy is released. If it's controlled in a device like a nuclear reactor it can provide power that is useful for many people today. This power can be used in homes, schools, and hospitals. Nuclear power plants require a lot of technology to be made but when completed they become a clean source of energy. Nuclear power plants produce clean energy that does not pollute the air or emit greenhouse gases.
But nuclear energy can also be bad.
If nuclear energy is not controlled it can create dangerous weapons like the atomic bomb.