Diodes - explanation please?

[igorbog]

Hi
could you please explain when I use each type of diodes and what are important parameters for each diode type:
Schottky Diode
Zener Diode
PN DIode
SCRs & TRIACs
I'm looking for a short explanation. Thanks

 

[barry]

Schottky: Low forward voltage drop
Zener: Fairly constant breakdown voltage vs. current (used as a voltage reference)
SCRs and Triacs: Will conduct only when a trigger/gate voltage is applied. SCRs conduct in only one direction(like a diode); Triacs coduct in both directions.

When you say "PN diode", do you mean PIN diode?