A Zener diode is a special type of semiconductor device that allows current to flow in the reverse direction when a specific voltage, known as the Zener voltage, is reached. This unique property makes Zener diodes essential for voltage regulation in various electronic circuits. Zener diodes are widely used in power supplies and voltage reference applications. They help maintain a stable output voltage, protecting sensitive components from voltage spikes. By utilizing the breakdown voltage characteristic, Zener diodes ensure that electronic devices operate safely and efficiently.