Don Cooper , May 16, 2011; 06:31 p.m.
Lenses with the 'G' designation don't have an aperture ring. Aperture has to be set through the camera. AFS lenses have the focusing motor built into the lens. Usually much quieter and faster focusing than regular AF lenses that have the focusing motor in the body and mechanically focus the lens. AFS lenses will not autofocus on AF only bodies. Bodies that are AFS only will not autofocus with regular AF lenses.