In general, a reserve (specifically, a commercial bank reserve) is a monetary amount that is created and put aside in order to meet specific requirements, including, for banks and financial institutions, central bank requirements. The institution either keeps its reserves (real paper money) in its vaults or in its account at the central bank.

Central bank reserves constitute one of the three categories of money issued or maintained by a central bank (a reserve bank). Such reserves are created by a central bank (reserve bank) in order to facilitate payments between financial institutions within its jurisdiction. Another important component of central bank reserves is gold that represent a safe holding, in addition to its liquidity and return characteristics. Central banks have significant holdings of gold as a type of reserve, roughly accounting for a fifth of all the gold that has been mined throughout history (2023 figures).