Laser fusion is a form of Inertial Confinement Fusion (ICF). If you want to break those words down, you would have the following three ideas put together -
Inertial – In other words, it has to do with inertia (the tendency of an object that is in motion to stay in motion). So we're starting with objects that are in motion, and that we want to keep in motion.
Confinement – We all know what confine means. So now we're looking at objects that are both confined and are in motion.
Fusion – This is when two things combine...in nuclear fusion, atoms are combined to make energy. In nuclear fission, atoms are split to make energy.
All together now, that leaves us with a bunch of atoms, moving about in a constricted area, bumping into one another and fusing together. And how do we accomplish it? Lasers. Hence, we have—Laser Fusion.