Boy, are you on a roll today. You got me on the floor again with that one.
Robb, assuming you're serious, "pre/pro" stands for
pre-amplifier/
processor. It's called that because it "
processes" the incoming signal from a source (cable box, DVD player, etc.)
previous to the signal being sent to the amplifier (pre-amplifier). A separate pre/pro has no amplifier. It must be used with a separate amplifier. A receiver is both a pre/pro and an amplifier in one box. A receiver with pre-outs can bypass it's built in amplifier section and, after processing the signal, send that signal to a separate amplifier, thus acting just like a separate pre/pro.