- An LED is basically a really fancy diode. Diodes only let current (electricity) to flow in one direction and not the other. LEDs are diodes too, but they have the unique 'side effect' of producing light while electricity is flowing through them." And if it's LEDs you want, it's LEDs you'll get: intricate descriptions of various types, detailed performance tests, lengthy discussions of incandescent vs. LED flashlights, and more.