fusion = the combination of two hydroegn isotopes to create a helium isotope

cold fusion = doing the above without needing to use an a-bomb first,

controlled cold fusion - keeping above reactiosn stable enough and not getting plasma all over your shoes (woul be used for nuclear power)

fission - smashing uranium and neutrons together to release small amounts of energy (splitting the atom actually gives off not alot of energy at all, splitting billions of atoms on the other hand is quite powerful)

controlled fission - using various rods to control a fission reaction so it doesn't explode, (absorb neutrons so the whole thing doesn't detonate at once) this is what we know as nuclear power