It means one or more of your rear lights (not just brake lights) are out. The thing that Deadly Sushi is referring to is the loom of wires inside the trunk by the driver's side trunk hinge. The wires in that loom tend to fray and break over time, causing some problems with the rear lights. However, don't just assumne that is the problem. Go through and check all the rear bulbs and sockets first. Also, don't forget the high mounted brake light.