The German Bundesbank virtually dictated Germany's position in the negotiations leading to the Maastricht treaty. It forced the hands of its co-signatories to agree to strict terms of accession into the Euro single currency project. It is an irony of history that Germany itself is not eligible under these criteria and cannot be accepted as a member in the club whose rules it has assisted to formulate. But all these constitute a secondary and marginal portion of a central banks activities. The main function of a modern central bank is the monitoring and regulation of interest rates in the economy.
Interest rates is supposed to influence the level of economic activity in the economy.
This supposed link has not unequivocally proven by economic research. Also, there usually is a delay between the alteration of interest rates and the foreseen impact on the economy. This makes assessment of the interest rate policy difficult. Still, central banks use interest rates to fine tune the economy. Higher interest rates - lower economic activity and lower inflation.