Light amplification by stimulated emission of radiation is the full meaning of the acronym

LASER (Light Amplification by Stimulated Emission of Radiation)

A laser is a device that works by the principles of optics that emits a monochromatic light beam (of a single wavelength), coherent and with high intensity. Being this possible thanks to the electrical or thermal stimulation of  atoms of a specific material and, on which the color of the emitted light will depend.

Basically, this instrument concentrates the light in a narrow beam and emits it in a concentrated and coherent form.

kepler used the data from tycho blahe (his mentor) to construct the laws of planetary motion.