The Light Emitting Diode or LED for short, is a two-lead semiconducting device that emits light when a certain amount of current is passed through. When using a LED, we need to be very careful not to apply too much current because it is very easy to blow one. For most LED, the recommended voltage would be 5 volts.
Most LEDs have two different size connectors. The long connector is the anode and should be connected to a power source. The short connector is a cathode and should be connected to a common ground.