A diode is used as a one way switch. This means that it allows the current to flow in a direction, but does not let it flow in the opposite. That is the function of a normal diode, but diodes can be modified to do different functions, light a LED. LEDs (Light Emiting Diodes) are essentially semiconductor devices that emit light when current passes through them. Now, how much energy do diodes and LEDs use? A diode uses around 0.5V or 0.8V, A LED uses between 1.8 and 3.3 volts, as as we can see in this simulation: seen in the simulation: Tinkercard Simulation Tinkercard circuits simulator Symbol of a LED Symbol of a diode Real LED Real Diode
