Monetary and fiscal policy are tools used by governments to influence economic activity. Monetary policy refers to actions taken by central banks to influence the supply and cost of money. Key instruments of monetary policy include bank rates, open market operations, and reserve requirements. Fiscal policy involves manipulating taxes and government spending to achieve objectives like full employment and price stability. During inflation, fiscal policy aims to reduce aggregate demand, while during depressions it aims to increase demand through deficit spending and tax cuts.