Okay, I'm building a serial link cable for my TI calculator and the plans call for two zener diodes. What exactly is a zener diode? Is that just a regular diode, because I have some diodes, and if ...

The lowly diode, a device with only two leads, can nonetheless do many things. Diodes can detect, rectify, suppress, emit light, detect light, change capacitance, emit microwaves and more.