Curious about Canon wireless flash

[agb]

I have read that the canon wireless flash is an optical not IR or radio communication between the camera and the flash head. In my Canon 7D manual, 119, and pg 121 it mentions setting the channel to 1 to 4 to match the flash, and in the 580EXII manual it again mentions setting, on page 37 and on page 40 that the channel has to be set to the same as on the camera to prevent signal confustion.
So although I do not need to know what these are to be able to work them I was just curious.

[ElectricImages]

Um... curious about what, exactly? :p

[agb]

Um... curious about what, exactly? :p
What are the channels, radio ,IR, can't possibly be different visible light waves ? What frequency? Just what are these channels?

[reaction]

I'm sure there's a question in there, I just don't know what it is.
well must be different right, or else it would be the same.