OLED is the abbreviation for Organic Light Emitting Diode. OLED displays are utilizing so called sogenannte Light-Emitting Polymers (LEPs) which can be described as organic dyestuffs that start to illuminate once they are activated by an electronic impulse.
Just like LCDs, an OLED display is made up of several thousand pixels. Each pixel consists of three sub-pixels of the colors red, green and blue. All the other colors are created by mixing these three ground colors at various ratios. You can obtain more information on the topic of OLEDs in this Special.