I see these terms often in posts and am not always sure what exactly is being talked about. What is the "cab" light? Is that just another term for the dome light inside the cab? Seems I have seen that mentioned with regard to bed lighting and I don't see what that would have to do with bed lighting. Is there some light (maybe on the back of the cab) that lights up the bed of the truck? If so, how do you turn it on? Is it part of the third brake light assembly?