you get updated textures, models, graphics, a shitload of cool features that standard QW doesn't have like brightskins, server browser, and a whole bunch of other awesome stuff. And you can pretty much tweak everything from the GUI too.
Contains configs(Useable in any Quake based engine). Also a keyboard menu for Gold Source and Source (Half-Life tech). You can look at the keyboard manually if you don't own any games based around the engine.