This document outlines the properties and applications of diodes. It begins with a brief history of diode discovery in 1901 by an Indian professor. A diode is then defined as a two-terminal semiconductor device that only allows current to flow in one direction. Common diode types include light emitting diodes and rectifying diodes. Diodes have a wide range of applications including use in communication systems, computers, power supplies, and television systems as rectifiers, limiters, and detectors.