Common displays are divided into four types: CTR display, LCD display and LED display.

1. CRT display is a display using a cathode ray tube, which is usually one of the standard equipment of a computer. The early CRT display only had a small piece of green, but now the 20-inch CRT display is common. With the increase of size, the most visible effect of CRT display is also improving.

2. Liquid crystal is a special substance between solid and liquid. It is an organic compound, which is liquid in normal state, but its molecular arrangement is as regular as that of solid crystal, so it is called liquid crystal. Another special property of liquid crystal is that if an electric field is applied to it, it will change its molecular arrangement.

At this time, if it is matched with a polarizer, it will have the function of preventing the light from passing through (when the electric field is not applied, the light can pass through smoothly). If it is matched with a color filter and the voltage applied to the liquid crystal is changed, the amount of light transmission of a certain color can be changed. It can also be vividly said that changing the voltage at both ends of the liquid crystal can change its light transmission (but in practice, this must be matched with the polarizer).

3. LED panel is a display screen used to display various information such as text, graphics, images, animation, market, video, video signal, etc. by controlling the display of semiconductor LED.

Through proper connection (including series and parallel connection) of LED chips and appropriate optical structure. The light emitting section or light emitting point of the light emitting display can be formed. These light-emitting segments or points can form digital tubes, symbol tubes, meter tubes, matrix tubes, level display tubes, and so on. Generally, the nixie tube, symbol tube and meter tube are collectively referred to as the stroke display, while the stroke display and matrix tube are collectively referred to as the character display.