I used to have a cheap Acer keyboard that had two USB ports in the back, so it acted as a little bonus USB hub that you could plug extra stuff into. Great for q

I used to have a cheap Acer keyboard that had two USB ports in the back, so it acted as a little bonus USB hub that you could plug extra stuff into. Great for quick USB drive transfers; you could even plug in your mouse there. For a second I thought that's what Apple meant here. But they just mean you can plug in the device itself.