FACTBOX-What is quantitative easing?

Dec 23 (Reuters) - Bank of Japan Governor Masaaki Shirakawa said last week that the central bank's decision to cut interest rates and buy more assets did not mark a return to quantitative easing, an extreme policy Japan used between 2001 and 2006.

But what is quantitative easing? Here are some details:

WHAT IS QUANTITATIVE EASING?

-- Quantitative easing refers to ways of boosting economic growth after traditional monetary policy tools, such as interest rate targets, have been exhausted.

-- Central banks flood the banking system with masses of money, more than is needed to keep official interest rates at zero or a low rate, to shore up financial systems and promote lending. They usually do this by buying up large quantities of assets from banks.

WHO HAS USED IT?

* JAPAN: