Amp with speaker INPUTS?? Please explain!

So, I was browsing an amplifier manual, as one does, and the diagram shows four spring clips (R+ R- L+ L-) labeled Speaker IN. (I couldn’t figure out the image hosting thing, otherwise I’d post pics. It’s an AudioSource Amp 300, and the manual is short and easy to find.) I’m not familiar with component connections beyond a couple pairs of speakers and maybe an EQ. But this puzzles me. Can someone please explain when you’d use this? The short “explanation” In the manual is woefully inadequate. 
 

I’m especially interested to know if speakers are at the other end of the wires that connect here. I mean, that would make no sense since speakers don’t send anything that direction, right?