A diode is semiconductor device which is used in a lot of application in electronics equipment.it is negative temp. coefficient device i.e. at lower temp. it is behave like a insulator and high temp. it is work like a good conductor.
Basically a diode is used to convert an alternating current into direct current in form of a rectifier.
There are many types of diode used in today day to day life depends upon their application.
1 crystal diode
2 photo diode
3zener diode
are some of the most useful diode.