Why is zener diode used as a voltage regulator?

Zener diode has the property of behaving like a dc battery in ‘on’ state (i.e. when the voltage across the zener diode exceeds its zener voltage rating VZ) . In ‘on’ state , the voltage across zener diode remains constant until the voltage across it deops less than VZ . This property of zener diode makes its use as a voltage regulator.