Simply speaking, a laser produces a concentrated light beam whose photons (light particles) are emitted in a synchronized manner. In general, there are two mirrors in a laser, with one being partially opaque. The latter lets light enter when the photons, which have been reflected several times between the two mirrors, have reached an energy level that is sufficient to allow them to go through the semi-opaque mirror.
There are different classes of lasers, some of which are forbidden on the market for personal use. This is not surprising since lasers can produce strong radiation, set things immediately on fire, cause blindness, pierce metal and even sculpt diamonds!