A TFT-LCD panel is comprised of two substrates, one in the front and the other in the back. The front substrate is fitted with a color filter (CF) to create colors. The back substrate is where the TFT (thin film transistor) arrays are deployed to control the pixels. Sandwiched in between the two substrates is a liquid crystal layer. The liquid crystals rotate in different angles according to the charges applied to each of them, adjusting the transmission of light from the backlight unit to display the gray-scale. A matrix of RGB pixels is usually located on the CF substrate, corresponding to the TFT array on the backplane. Colors and brightness are achieved by mixing the RGB pixels with different gray-scale levels.
The backlight unit is situated behind the TFT-array panel, providing the light source and driving the circuit board to control the voltage for the panel.