Rubber/Plastic shades prevent light from entering the lens from extreme angles, giving sharper, clearer pictures and better color. Can be folded back and left on camera even when the case is closed. Double threaded to accept filters.
Lens hoods are primarily designed to prevent unwanted stray light from entering the lens by extending and shading the end of the lens. In addition, since the end of the lens is extended you also get the added benefit of some extra protection from accidental impact.