What is wrong with the lights on a 92 cadillac sts if the front headlights work but and the tailights but not the brake lights or the blinker?

THERE IS A BREAK SWITCH FOR BREAK LIGHTS , THERE IS A FLASHER FOR TURN SIGNALS . THERE IS A SEPERATE FUSE FOR EACH . SINCE YOU SAY YOUR PROBLEM IS IN THE BACK I ASSUME THE FRONT SIGNAL WORK THAT ELIMINATES THE FLASHER AND FUSE , SO RIGHT NOW I SAY LIGHT BULBS .