Fission is the splitting apart of heavy nuclei.
Electron beams are sent into a nucleus of uranium, for example, and the nucleus splits releasing large amounts of energy. Fusion is just the opposite, light atoms are joined to form a heavier one. Magnetic confinement involves holding a sufficiently hot, dense plasma with powerful electromagnetic forces, so that fusion can occur, but over a suitably long time. Inertial confinement is when a powerful beam is used to hit a small pellet of fuel for a fraction of a second which heats and compresses the fuel until fusion occurs. These beams can be produced by either laser or electron beam generators.