An LED emits light when current flows through it, while a regular diode does not.

An LED, or light-emitting diode, is a specialized type of diode that generates light during current flow. This phenomenon is known as electroluminescence, where electrons within the semiconductor material recombine with holes, releasing energy in the form of photons. LEDs are widely used in various applications, including lighting, displays, and indicators, and they are significantly more energy-efficient than traditional incandescent bulbs.

In contrast, a regular diode is designed to permit current flow in only one direction. When a voltage is applied in the forward direction, the diode conducts current; however, when the voltage is reversed, the diode blocks current flow. This characteristic makes diodes essential components in rectification circuits, which convert alternating current (AC) voltage to direct current (DC) voltage.

Although both LEDs and regular diodes are constructed from semiconductor materials like silicon or gallium arsenide, LEDs are engineered with a specific structure that facilitates efficient light emission. This structure typically consists of layers of different materials, such as a p-type layer and an n-type layer, which form a junction where electrons and holes can recombine to produce light.

In summary, the primary distinction between an LED and a regular diode is that an LED is specifically designed to emit light, while a regular diode is intended solely to control the direction of current flow.