Acronym for Light Amplification by Stimulated Emission of Radiation. For most of us, a laser is a device that produces a very focused beam of light (or electromagnetic energy), usually of a very narrow bandwidth in terms of wavelength. In very simple terms it means very focused and directional energy. A laser is a nearly coherent light source, meaning all the energy emitted is completely in phase, of the same frequency (color), and polarization. It projects in a narrow straight line, as opposed to radiating in more of an omnidirectional way like a standard light bulb. Thus nearly all of the energy present can be focused on a single point where the beam stops. This property allows lasers to be used in many industrial and medical applications. Of those, the ones we are interested in is use writing (burning) and reading optical media such as CDR, CD-RW, and DVD. This is accomplished by burning or reflecting the beam off of previously burned transitions from pits to land in optical media.