Quantitative easing is a process that involves a country's central bank printing a lot of new money, in order to increase the supply of money. 'Quantitative' refers to the money supply; 'easing' essentially means increasing. Quantitative easing is a tool of monetary policy.
Quantitative easing was used notably by the Bank of Japan to fight domestic deflation in the early 2000s. In this case, the Bank of Japan flooded commercial banks with excess liquidity to promote private lending, leaving them with large stocks of excess reserves, and therefore little risk of a liquidity shortage.
