First of all, we have to understand what money is in our society nowadays. Money is neither gold, nor silver, nor anything with physical existence. Money is simply an IOU (I Owe You), a debit or credit entry in the account books of banks.
The IOU of the banks are gathered (or cleared) in the Central Bank as debit or credit entries. Most Central Banks would charge interest on debit entries (those who are debtor banks), called "discount rate", but gives NO interest to credit entries (those who are creditor banks).
Because the creditor banks get no interest from the Central Bank, they would lend to the debtor banks at a lower interest rate than the discount rate. And this is called "Inter-bank Money Market". It is a win-win situation, the Creditor Banks get some interest, and the Debtor banks pay an interest lower than the "discount rate" charged by the Central Bank. If you wish to understand more, click my webpage on Money.
Because money is IOU, it is limitless in supply. Should money be gold or silver, their supply is limited, but not IOU. Therefore someone once said, "If I were a banker, I would make the biggest bet. If I win, I go home a millionaire. If I lose, the IMF (=International Monetary Fund) will bail me out."
Also because money ( = IOU ) is handled by computer, fraud is extremely easy.
Wu Siu Yan