How does a laser work

Energy supplied to the material the laser is made from causes electrons to become excited a photon of light stimulates these electrons to drop down to a lower energy level, releasing more photons these photons have the same frequency, same direction and are in phase with the photon causing their release, so are coherent more and more photons are emitted, creating the laser beam part of the beam is reflected back inside the laser energy is supplied to the laser to cause electrons to go back to a higher energy level. The reflected photons are used to keep the process going.