What specifically does the red BRAKE warning light mean in a 2002 VW Cabrio?

I don't have a manual for my 2002 VW Cabrio. The brake warning light just came on - The word BRAKE in red capital letters. Is this a brake fluid problem, a sensor problem, etc.? The parking brake isn't on, and it drives and brakes fine. Just had my brake pads changed in March of '08, so that shouldn't be the problem.|||Brake warning lights come on when you are low on fluid. Also, in some vehicle them come on for a few seconds when the vehicle is started. It could also be a sensor problem. I would take it to a shop, and they will be able to plug into the computer and read what the computer says is wrong. |||Could be 2 problems, parking brake engaged or low fluid in the master cylinder. |||it could be any of the above, low fluid level,a pressure difference in the two halves of the system, a brake lamp that is out, an e brake that is still partially on, or pads that have worn to a minimum. my best advice is that you get the brakes checked out by a professional.