Fusion power is a way of generating energy by using nuclear fusion reactions. For the moment, this is only theoretically possible, but a lot of research is invested in developing real fusion power plants.

The preamplifiers of the National Ignition Facility are the first step in increasing the energy of laser beams as they make their way toward the target chamber. NIF recently achieved a 500 terawatt shot - 1,000 times more power than the United States uses at any instant in time. Photo credit: Damien Jemison/LLNL, via Wikipedia
Fusion power definition

The nuclear fusion reaction, which is at the base of generating fusion power, is a reaction in which at least two atomic nuclei are combined together. As a result, new atomic nuclei and several subatomic particles (neutrons and protons) are produced. The energy produced is the difference in mass between the nuclei that entered the reaction and the final products.

Fusion energy is real and it occurs in stars, all over the universe.