Laser is a word formed from the acronym "Light Amplification by Stimulated Emission of Radiation."
Light from a laser is both temporally coherent, meaning it is of a single pure color, and spatially coherent, meaning that it can be easily formed into a thin beam or focused to a small spot. The angle at which a laser beam spreads is determined by diffraction; a wide beam will diverge more slowly than a narrow beam. Many cheap laser pointers exhibit excess beam dissipation due to cheap manufacturing, and shoddy construction.
The use of lasers is very important in science and medicine; they have also become ubiquitous in CD-ROM and DVD players and as pointers.  They're also used in bar code scanners. In recent years, lasers have even become a seemingly effective weapon for certain militaries. They seem effective against a variety of targets, including planes, missiles, and ground vehicles.