Lasers make very pure, intense light. Remember that light is made of waves. Normal light has many waves all bouncing around at different times. It looks like a choppy lake on a stormy day. Lasers are different. In a laser, all the waves bounce at the same time. The light is called coherent. Laser light is usually one single color, but sometimes a few colors can be mixed together. Normal light is a mixture of many colors (see Prisms).
A laser works just like a fluorescent light. Inside a laser there is a tube filled with gas. When electricity flows through the gas it lights up. By using mirrors inside the tube, the light is made to bounce back and forth many times making it stronger and coherent.
Light can only be seen if it reflects off of something so you can’t normally see laser light. If there is some dust in the air, then a very fine laser beam can be seen. Another way to see a laser beam is to shine it into a light pipe (or light guide). A light pipe is clear plastic or glass. When light shines into it, the sides of the light pipe act like many tiny mirrors. The laser beam reflects off the sides and can travel from one end of the tube to the other before it gets out. It can even travel in a curve, something light can’t normally do.