The word laser is an acronym or abbreviation for light amplification by stimulated emission of radiation.
A laser beam is a single wavelength light, coherent or focused and therefore can travel over vast distances. Laser is created when the gases in a chamber are excited into a non-equilibrium condition, thus when a photon of light is introduced into the excited mix of gases a coherent radiation is produced.
Lasers may operate in a continuous wave mode or in a pulsed mode. In the latter situation, the energy that results is stored or halted and suddenly released in a controlled sequence.
When laser beams are focused onto tiny spots, they can be put to vast array of applications or uses - medical, printing, communication, military, cutting and engraving, and so forth.
Image credit: National Ignition Facility, CA, USA