central bank
is not a regular bank;
it is a government agency, and
it stands at the cen- ter of a country's monetary and nancial system.
they have helped to guide the develop- ment of modern nancial and monetary systems and they play a major role in economic policy.
virtually all countries have central banks: the Federal Reserve in the United States, the Bank of Japan, the Bank of Canada, and so on .

currency union, where a number of countries collectively share a central bank. By far the most important example of that is the European Central Bank, which is the central bank for seventeen European countries that share the euro as their common currency . each of the participating countries does have its own central bank, which is part of the overall system of the euro.
What do central banks do
achieve macroeconomic stability. By that I mean achiev- ing stable growth in the economy, avoiding big swings—recessions and the like—and keeping in ation low and stable
keep the nancial system working normally
try to either pre- vent or mitigate nancial panics or nancial crises

What are the tools that central banks use to achieve these two