A diode is a semiconductor component that mainly allows current to flow in one direction. It blocks current in the opposite direction under normal conditions.
Why diodes matter
Diodes are used to convert AC to DC, protect circuits from reverse polarity, steer signals, clamp voltage, and build switching circuits. A light-emitting diode, or LED, is a special kind of diode that produces light.
Forward and reverse direction
When a diode is forward-biased, current can flow. When it is reverse-biased, current is mostly blocked unless the voltage is high enough to break through the diode's limit.
In simple terms, a diode gives current a preferred direction.