Sports Gurus: Why was Jerry Rice so special on the field?

I know he was great at route running and had great hands, but I never really heard about him being a speedy or tall physically dominant receiver… How did he seem to be so open and behind corner backs and safeties on the field? (At least on his highlight tapes) was he a deep threat only kind of guy? Or did he do most of his work with more mid field receptions than up the side line?