Quantitative easing (QE) is a monetary policy used by some central banks to increase the supply of money by increasing the excess reserves of the banking system, generally through buying of the central government's own bonds to stabilize or raise their prices and thereby lower long-term interest rates. This policy is usually invoked when the normal methods to control the money supply have failed, e.g. the bank interest rate, discount rate and/or interbank interest rate are either at, or close to, zero.
The central bank then purchases financial assets, including government bonds, agency debt,mortgage-backed securities and corporate bonds, from banks and other financial institutions in a process referred to as open market operations. The purchases, by way of account deposits, give banks the excess reserves required for them to create new money, and thus hopefully induce a stimulation of the economy, by the process of deposit multiplication from increased lending in the fractional reserve banking system.
Risks include the policy being more effective than intended or the risk of not being effective enough, if banks opt simply to sit on the additional cash in order to increase their capital reserves in a climate of increasing defaults in their present loan portfolio.
"Quantitative" refers to the fact that a specific quantity of money is being created; "easing" refers to reducing the pressure on banks. However, another explanation is that the name comes from the Japanese-language expression for "stimulatory monetary policy", which uses the term "easing".Quantitative easing is sometimes colloquially described as "printing money" although in reality the money is simply shifted to member bank dollar deposits from financial instruments. Examples of economies where this policy has been used include Japan during the early 2000s, and the United States, the United Kingdom and the Eurozone during the global financial crisis of 2007–the present, since the programme is suitable for economies where the bank interest rate, discount rate and/or interbank interest rate are either at, or close to, zero. (content taken directly from Wikipedia )