Monitors for computers have come a long way since the first PC. At first they were all monochrome cathode ray tube, CRT, devices. A CRT is a large tube with a curved front tapering back to a small neck with the electronic parts in it. All the air is removed from the tube and a large negative electrical charge is applied to a heated plate call the cathode. This is the cathode. The far end or front is charged positively. this causes the electrons at the negative end to fly to the positive end creating a electron beam. This is controlled with several metal screens called grids. By controlling the stream it draws the image we want on to the back of the glass front of the CRT that is coat with a chemical called phosphorus that glows when struck by electrons. This is the image we see.
A color CRT is a more complex version of the monochrome CRT. Both of these use a lot of power and take up much of the desk top. To solve these problems the liquid crystal display or LCD was created. The LCD or, flat panel display, which is the more common monitor being sold today uses far less electricity and takes up much less of the desk top. The LCD monitor creates the colors by using a electrical charge to turn on or off the individual pixels of the image. They are lit from behind by a series of high output lamps the have a diffuser over them to evenly distribute the light.