LED

Short for Light-Emitting Diode, LED is a special type of semiconductor that illuminates when an electrical charge passes through it. LEDs are commonly green or red; however can be an assortment of other colors. A good example of a LED is the led status indicators on your keyboard for Num lock, Caps lock and Scroll Lock as shown in the below picture. In this pciture the blue LED is lit on the keyboard to indicate the Num Lock is enabled.

Also see: Access light, Amber, Electronics definitions, Green, OLED, Orange, Red