Quantitative easing is an unconventional monetary policy tool involving large-scale asset purchases by a central bank to increase the money supply and lower long-term interest rates. As an academic concept and policy approach, it investigates the transmission mechanisms through which central bank balance sheet expansion influences financial conditions, economic activity, and inflation, particularly when conventional interest rate adjustments are constrained. Its key characteristics include the direct injection of liquidity into the financial system and the manipulation of asset prices and yields beyond the short term, holding significant significance as a tool for economic stabilization during severe downturns.