Somebody always asks a question about laser weapons.
It is just a lot of energy concentrated on one spot, which heats up whatever it's shining on. This makes lasers an ineffective weapon to use against a person, for a person will usually move out of the way as soon as they feel a burning. Another consideration is that lasers are very inefficient, i.e. most of the power going into the laser doesn't emerge in the beam. This is because the light coming out of the laser is coherent, that is, all the light waves are in phase. When this coherent light strikes a rough surface, such as paper or the wall, it scatters and creates an interference pattern, which is the speckle.