Deposit account (How banking works) - Wikipedia
Typically, a bank will not hold the entire sum in reserve, but will loan most of the money out to other clients, in a process known as
fractional-reserve banking. This allows providers to earn interest on the asset and hence to pay out interest on deposits.
By transferring the ownership of deposits from one party to another, banks can avoid using physical cash as a method of payment. Commercial bank deposits account for most of the
money supply in use today. For example, if a bank in the United States makes a loan to a customer by depositing the loan proceeds in that customer's checking account, the bank typically records this event by debiting an asset account on the bank's books (called loans receivable or some similar name) and credits the deposit liability or checking account of the customer on the bank's books. From an economic standpoint, the bank has essentially created economic money (although not
legal tender). The customer's checking account balance has no dollar bills in it, as a demand deposit account is simply a liability owed by the bank to its customer. In this way, commercial banks are allowed to increase the money supply (without printing currency, or legal tender).