LED stands for light-emitting diode. It is a diode that produces light when electric current flows through it in the correct direction.
Why LEDs are common
LEDs are efficient, compact, fast, durable, and available in many colors. They are used in displays, indicators, lamps, keyboards, screens, remotes, traffic lights, and decorative lighting.
LEDs need current control
An LED normally needs a resistor, driver, or current-control circuit. Without current limiting, the LED can draw too much current and fail.
LEDs are polarity-sensitive, so the positive and negative sides must be connected correctly.