If the light is on *while driving*, it indicates a problem with the ABS system. However, the brakes themselves will still function, though without the anti-lock feature. If the light is *off* when the engine is running, your Jeep Liberty likely has ABS and it's functioning correctly.
If you can't locate the light or are unsure about its meaning, consult your Jeep Liberty's owner's manual. It will show you the location of all the warning lights and explain their meanings.