What is a backlight?

Backlights are the light-emissive components positioned behind the LCD cell. Backlights are a
part of all transmissive or transflective displays. When an LCD display is used in an environment
where the ambient lighting will not support good reflective-mode visibility, the backlight
luminance is required to give the display contrast and be legible. Backlights are also required
in almost all full-color TFT displays due to the inherently low efficiency of the transmissive
structure of the TFT cell.