What do the bizarre symbols mean?

"Play /Pause" makes sense, but why are there 4 of them?
"+" and "-" what are those? volume or channel? And there are two of those.
"Menu" makes sense, but there are two of them. Why? what's the difference?

Then, there are these: "I<<" and ">>I", also two of each.

The apple remote itself is very simple: up, down, left right, select, menu, and play/pause.

The the 412 codes correspond to the Apple remote?

thanks,
~Jay