What's wrong with my brakes?

Did the rear brakes lock up and you slid into them or was it the fronts ?

Anti lock system failure. You need to have it checked by someone who knows what they are doing, and not the dealer, find a good independent shop in your area to take it too. They will pull the codes and check the system over then tell you what it needs and a decent estimate of the cost.

Yes, the ABS system is really sensitive and if not maintained properly, it decays and fails. With ABS, you need to replace the brake fluid every eighty-thousand miles or six years, and the manufacturer recommends every thirty-thousand miles or two years. So I'm guessing you still have the original twenty-year-old brake fluid in the car and the brake peddle has felt spongy for a few years already.