This warning message means your rechargeable li-ion battery is near depletion or almost out of charge.
Power off your FZ53 and connect the supplied USB cable to the supplied AC adapter and plug into a wall socket. The other option is to charge your FZ53 with the supplied USB cable via your computer.
The indicator light will remain red until fully charged. At that time the indicator light/lamp will turn green and the FZ53 battery is fully charged and ready to use again.