This article explores different aspects of monetary policy using theoretical and econometric approaches. It discusses optimal monetary policy, credibility, reputation, the demand for money, causality analysis, and the effects of monetary policy on various economies. The researchers analyze the relationship between money and income, interest rates, inflation, and financial linkages in different countries. Key findings include the dynamics of the demand for money in the US, the relationship between money stock and monetary base in France, and the effects of monetary policy on business loans in the US.