The word laser is an acronym for "light amplification by stimulated emission of radiation." In a laser the lasing medium is charged to get the atoms into an excited stage. Very intense flashes of light or electrical discharges charge the lasing medium and create a large collection of excited-state atoms. Once the laser medium is charged, it contains atoms with excited electrons. The excited electrons have higher energies than the relaxed ones.

Just as the electron absorbed some amount of energy to reach this excited stage, it can also release this energy. Released energy comes in the form of photons or "light energy". A lasers'
Light is different than the light of a normal flashlight. The light released from a laser is monochromatic. Monochromatic contains one specific wavelength of light.

The light emitted is coherent (or in an organized form). The photon the atom releases has a certain wavelength. The other thing to a laser is a mirror at each laser medium. Photons reflect off these mirrors to travel back and forth through the laser medium. The mirror at one end is "half silvered", meaning it reflects some light and lets some through.

The laser in your CD player is a semiconductor laser. Lasers are classified in four areas. The areas include: Class I, Class IA, Class II. Others are Class IIIA, Class IIIB, and Class IIII. Some lasers are very powerful. The CO2 laser can cut through steel.