A rectifier diode is a semiconductor device that allows current to flow in one direction while blocking it in the opposite direction. This property makes it essential for converting alternating current (AC) to direct current (DC), a process known as rectification. Rectifier diodes are commonly used in power supplies and various electronic circuits. These diodes are typically made from materials like silicon or germanium and are designed to handle high voltage and current levels. They come in different types, such as standard rectifier diodes, Schottky diodes, and Zener diodes, each serving specific applications in electronic devices.