hmm, yeah, i really dont know what he means either, but 90% of the USB keyboards that you can buy in a store will work on mac. Just like 90% of the USB keyboards that you can buy in a store will work on a PC.
F12 is always eject, whether there is an eject symbol there or not.
As for keyboards... The majority of USB keyboards will work for you. I don't think you can convert a keyboard between USB and PS/2. I could be wrong. I do know you can convert a USB mouse to a PS/2 mouse