Short is the screen + LCD module backlight +PCB Board + iron box!
Power terminal, the instrument display is LCD module, which has the status of CRT picture tube.
Other parts include a power supply circuit, signal processing circuit, and so on, of course, the shell or something.
Module consists of screen and backlight components. Two parts to be assembled together, but the work is independent of each other (that is, circuits are not related).
Even the LCD backlight is the principle component of surface light, light through the LCD screen to our eyes. Screen is processed according to the pixel to the light, to display the image.