Diode
An electronic component allowing current to flow in only one direction, known as rectification. It has two terminals called cathode (-) and anode (+), made from semiconductor material doped with impurities giving each type distinct electrical properties. Common diodes include silicon, Germanium, Schottky, LED, Varactor, Zener, and Rectifier types. Diodes are employed in numerous applications such as full wave rectifiers, signal mixing, voltage regulation, surge suppression, and indicator lamps. A semiconductor junction inside a diode operates as a barrier impeding charge carriers until a specific threshold voltage referred to as the "breakdown" voltage is reached, when charges start conducting across the diode allowing conduction.
References:
https://www.fluke.com/en-us/learn/blog/electrical/what-is-a-diode