What does a diode do in an electronic circuit?

A diode allows current to flow in only one direction and blocks it in the reverse direction, acting like a one-way valve for electricity. This property makes diodes useful for converting alternating current (AC) to direct current (DC) in a process called rectification. A light-emitting diode (LED) is a special diode that emits light when current flows through it in the forward direction. Distinguishing the diode's one-way behavior from a resistor (limits current both ways) or a capacitor (stores charge) is common on the Electronics subtest.