On December 31, laser light shows were part of major New Year's Eve celebrations from the Niagara Falls Winter Festival of Lights to First Night Santa Fe. Light travels in waves. It is part of the electromagnetic spectrum that includes radio waves, microwaves, x-rays and gamma rays. These waves are invisible to the human eye. Light is the part of the spectrum that stimulates the eye's retina, resulting in sight.
Lasers are possible because of the way light interacts with electrons.
Usually they jump right back, releasing the extra energy in the form of light. The energy levels or states can be imagined as rings or orbits around a nucleus. Electrons in outer rings are at higher energy levels than those in inner rings. Then it falls to the lower energy level and emits a pulse of light. The disturbing pulse and the dislodged pulse are in phase.