Ordinary light from the sun or an electric lamp, is a mix of many different wavelengths, or colors. Also the waves are jumbled and rise and fall out of step with each other. Laser light is different. Its waves are just one wavelength, or color, and these waves are all in step with each other, rising and falling together. The result is an intense beam of a single color, that does not spread out or fade like ordinary light. Laser light is even brighter than sunlight. It has so much energy that it can "burn" through metal. Lasers are used in hundreds of ways, in industry, medicine and surgery, to make holograms, to read bar codes and compact discs, and send messages along fiber-optic cables.
How a laser works
"Laser" stands for Light Amplification by the Stimulated Emission of Radiation. Laser light is made by feeding energy, such as ordinary light or electricity, into a substance called the active medium. As the active medium takes in the energy, its atoms start to release light of a particular wavelength. When light from one atom strikes its neighbors, they also release identical bursts of light. The light energy builds up as it is reflected to and fro by special mirrors at each end of the Laser. Eventually, the light becomes so intense that some of it escapes through one of the mirrors and forms the Laser beam. (World of Science)