There are different types of televisions available today:

Picture Tube CRT (Cathode Ray Tube).These are how TVs have been produced for the past 60+ years. They work by the CRT shooting an electron beam against a phosphor covered surface. When the phosphors get hit they glow. The TVs have red, green, and blue phosphors. These make up a color image.

Rear projection CRT works much the same way. They work by shining an image against a mirror and then onto a screen. The "guts" for the TV are at the bottom and the screen occupies the top two-thirds.

Front projection CRT works much the same way. These are a projector typically mounted to the ceiling with three lenses - red, green, and blue. Once these images are aligned on the screen they make up the color pictures.

Flat Panels come in several varieties.

LCD (Liquid Crystal Display). LCDs are the same basic technology as many calculator displays. LCDs have many tiny pixels or particles sandwiched between two pieces of glass. With no voltage their placement is random. When voltage is applied these pixels line up. By varying the speed at which they align and disperse you can get different shades of gray. Once red, green, and blue filters are added you can get full color video.

DLP (Digital Light Processing). DLPs work basically the same way except they use thousands of tiny mirrors on a single chip. Each mirror can be turned on or off to make a picture image. A color wheel is added on another chip to make color images. Or, some use three chips each with a color filter (these are currently just in the professional market). DLPs work digitally whereas CRTs and LCDs are analog devices.

Plasma Displays. Plasmas have individual red, green, and blue pixels aligned between two pieces of glass with a rare gas sealed within each pixel. When voltage is applied to the pixel it produces ultraviolet light. This light then strikes a red, green, or blue phosphor at the rear of the pixel causing it to glow.