Where does fusion regularly occur and what kind of energy is protected?

Fusion occurs inside the earth. It heats Magma, which can be used to heat homes or generate electricity

Fusion, however, is an odder beast. A fusion reaction requires a large amount of starting energy; enough to strip the electrons off of the deuterium/tritium nuclei and form plasma. That heat is also enough to accelerate the particles fast enough that when they collide, the initial electromagnetic repulsion is overcome and the strong interaction binds them together.