The voltage that a battery provides nominally, i.e. according to its designation.
Batteries must be selected so that the nominal voltage matches the voltage required by a vehicle or device in normal operation. For motorcycles this is normally 6 or 12 volts.
A battery with a nominal voltage of 12 V actually delivers a voltage of 12.72 V, consisting of 6 cells connected in series at 2.12 V each. The open-circuit voltage is measured when the battery has been disconnected from any charge for at least 4 hours and no current has been drawn for at least 1 hour.