OLED is short for organic light emitting diode. On the microscopic level, an OLED display is a matrix of organic LEDs that light up when they emit energy. Old LCD (Liquid Crystal Display) technology uses electronically controlled polarizers to change the way light passes or does not pass through them. This requires an external backlight that lights up the whole display underneath. This uses a lot of energy because at the time the display is on, enough light for all pixels must be provided.