"BRAKE" Warning light may mean low system pressure
Most Cars have one or two warning lights in the instrument cluster (Dashboard) that signals the driver that something is going wrong or something is just not right with your brake system.
When you first start the car, all your instrument lights should come on for a few seconds. This is a verification that the illuminated systems are being monitored and are now ready to be checked for proper operation. Once the system has verified a good operating condition, it is given a go, indicated by turning that system's light off. If any of these lights fails to illuminate on the initial start up, you may have a bad bulb or circuit. If a light comes back on, you have a problem looming and you need to take immediate action to remedy it.
A brake warning light may mean that your emergency brake is on and you need to release it or that you may have a brake system pressure failure in one of the two brake fluid sections. Your car's brake fluid is divided by two sections, each section controls two wheels. This is a built-in redundancy for safety, preventing a complete brake system failure in case of a ruptured brake fluid line. Have you ever seen a movie where the vilan crawls under the car and cuts the brake fluid line, resulting in the demise of the driver? Well, that is just not possible unless both system lines are severed, even then, the driver would feel an immediate problem with the car's brakes and stop from driving off.
ABS warning light illuminates if the system detects a malfunction
If you loose your brake pedal completely while you're driving, don't panic, calmly pull over to a stop by using your emergency brakes and have your brakes repaired.
Most cars nowadays have ABS (anti-lock braking system), if there is a problem with the ABS system, your yellow "ABS" brake light will illuminate and stay on. Your brake will function properly, you just won't have the anti-lock system enabled. You can safely drive it to your repair facility.