Strobist so overwhelmed!

[dtscds]

My VERY BASIC understanding of triggering off camera lighting.

Optical: (Sometimes referred to as master/slave). The master fires and it's flash sets off the other flashes you have set up. Since they need to actually "see" the flash that is why it is called "Optical". As Brad said it can be iffy. In a fairly dark place you would have less problems than outdoors in bright sunlight.

There is also Canon's "IR" system where you would have one flash mounted to the camera as the master and then it would send out a beam of Infrared light to other Canon flashes. Again, the slave lights must be able to see the beam so it is easily disrupted.
I know nothing about Nikon's ability to do this. I'm sure someone from that side will chime in and tell you how perfect Nikon's system works...

Radio wave triggers:
There are many brands but they all work on essentially the same principle. You attach a transmitter to your camera and a receiver to each flash. One transmitter can control as many receivers as you want--assuming they are all on the same frequency.

The more basic units--the Ebay triggers in their various forms and Pocket Wizards--just send out a signal that tells the flash to fire. You must set everything manually. The difference here is price/reliability. The Ebay triggers are dirt cheap but are known to misfire occasionally. The Pocket Wizards are very spendy but very reliable. The new CTR 301's are supposed to be very reliable and still pretty darn cheap. There are other brands out there but I don't know anything about them.

The newer versions of the radio triggers are incorporating the ability to use TTL technology along with the ability to move the flash off camera. TTL means that the camera diagnoses the scene and adjusts the flash to match conditions. Just like what the flash/camera does when the flash is attached to the hotshoe on the camera. Radio Poppers and the newest version of the Pocket Wizards do this. Again, very spendy. But, you get the benefit of the camera/flash setting everything for you on the fly.

Hope this helps...