Fission occurs when a neutron hits a nucleus and it splits to become 2 smaller nuclei and releases more neutrons
These neutrons can collide with other nuclei and cause more reactions which would be a chain reaction
Used for electricity as it doesn't produce harmful bi products
Risky as there can be accidents such as Chernobyl
Nuclear fusion is the joining of two light nuclei to form a heavier nucleus and releasing Neutrons. Good because there is no radioactive waste and produces heavy amounts of energy