Lasers, or Light Amplification by Stimulated Emission of Radiation, are devices that generate and amplify light waves through a process called stimulated emission. In a laser, a material called the gain medium is energized, causing it to emit light particles called photons. These photons can stimulate more photons to be emitted in a process called stimulated emission, which amplifies the light waves.

The light waves are then focused through a lens or a set of mirrors, producing a concentrated, highly directional beam of light. Lasers are used in a wide range of applications, including cutting, welding, medicine, and communication.