The brake light switch is stuck or out of adjustment. If it is a mechanical switch it is located somewhere on the brake pedal swing arm. If it is a pressure switch it is located near the Master Cylinder.
Brake lights draw their energy from the vehicle's battery.
Year? Brake lights on the car? The dash? I would suspect you have a problem with the brake system. Check the master cylinder to see if it is full. If so, take it to a professional for inspection.
Defective or misaligned brake light switch.
the connection between the battery and the brake lights
It means one of your rear brake lights are out. Not the tailights but the brake light(s).
Adjust or replace the brake light switch.
I had a similar situation with my 2000 Accord. The brake, battery, and door lights all came on and stayed on. I did a little research online and then called my dealer's service department to verify. There are two possibilities; the alternator or the battery. I could be as simple as needing to clean your battery terminal posts. I popped my hood and found a lovely shade of blue-green coating my connection. I cleaned it off and the lights went out. I probably need a new battery soon, but my lights went off!
its the brake resivior
You probably have a bad ground. Check the grounds on the brake lights.
Do you mean What does it mean when the brake and battery lights come on in when it is already started? Check your alternator may be its not working well it cause the battery sign comes out.
It may be a defective brake light switch. The location of the brake lights fuse is listed in your owner's manual.