It describes the portion of a currency (money supply) that is created out of book money – i.e., debt generated by commercial banks. It is that portion of money in an economy that is created by commercial banks through issuance of debt, which constitutes commercial bank liabilities in the form of deposits held at such  banks (which can be used for settlement and fulfillment of obligations).

Commercial bank money consists mainly of deposit balances that can be transferred either by using paper orders (such as checks) or electronically (e.g., debit cards, wire transfers, and online payments).

Certain electronic-payment systems are fitted to process transactions in multiple currencies.