A laser is a device that emits light from an electromagnetic radiation source.  The first laser was built in 1960 by Theodore Maiman at Hughes Research Laboratories, based on theoretical work by Charles H. Townes and Arthur Leonard Schawlow.

Lasers emit a certain type of light. Light that is coherent. Coherence can be measured spatially or temporally. Spacial coherence allows laser beams to stay narrow over great distances. Temporal coherence can be used to produce ultrashort pules of light. 

Some example of the uses of lasers are optical disc drives, laser printers, barcode scanners, fiber optics and photolithography