Nuclear fission is a nuclear reaction in which a heavy nucleus spontainiously splits or when it comes in contact with another particle (a nucleus), in which the nucleus creates a large radioactive reaction. This process can generate usable energy for everyday use. Radioactive elements are used to create this reaction. Nuclear reactors are used to maintain the energy.
Nuclear fission is somthing used in our daily lives. It provides lots of efficient and clean energy. That energy could be powering your house. There are currently 60 nuclear power plants in the U.S, providing 20% of our electricity.
Stefan Kühn, CC BY-SA 3.0 from wikipedia.org