A laser is a high-energy beam of light that can selectively transfer its energy into tissue to treat the skin.
Lasers contain a material that produces and amplifies light.
Two mirrors cause the light to reflect back and forth through this material. The result is a light beam that is collimated and intense. This light is either one pure color or several different pure colors. These properties which separate the laser from a light bulb, are important to the medical application of lasers. Many procedures cannot be done without the laser.