Great, thanks so much. :thanks....they are the same mount obviously, but essentially the D's have no internal motors or electronics.....they require an external drive (a tiny driveshaft in the camera body of the mounting ring) to control the mechanics of lense. The D90 & above has this ability whereas the lower line nikons don't. G lenses or 'CPU lenses' have internal motor drives
& generally have 'antivibration-antishake' vibration reduction systems also that help reduce image shake. G lense are newer than D....but the G will have several 'cpu contacts' on it's bottom ring & usually 1 or 2 electronic switches on the body. If you 90 came with the 18-105 zoom, that's a G lense. The d90 can run D and G lenses essentially identically, whereas the models below the d90 can only run D lense manually.