is happens 'just before' it becomes a Pro.... pre/pro
(Pre)amp
(Pro)cessor
just simply means the unit is both the preamp and processor in one device.
as far as hearing your speakers... they may make a sound without being hooked up to something but it may not be the sounds you want. haha
Do a web search on 'how speakers work' to understand how these things work. Or better yet... go to BestBuy and ask the gurus there to explain how it all works... they'll love that!