What is the zener point?

A diode (some people incorrectly call them rectifiers) is a semiconductor device that allows a current to flow in one direction. A Zener diode allows a reverse to current to flow at a defined voltage. A common application for them is as a voltage regulator. Named for C M Zener , US Physicist. A zener diode is a diode and like all diodes it will conduct in both directions. If a reversed voltage is applied it will breakdown and conduct current. Most diodes when they breakdown the reversed voltage cannot be predictable. However a zener diode when they do breakdown in the reverse voltage mode that voltage can be made as predictable and remain +/- % of the breakdown voltage. Therefore this steady voltage can be used as a regulator for instance or a definite voltage drop if need be.