A central bank is an organization responsible for managing banking activity. Within the USA the central bank is the Federal Reserve, or ‘the Fed’. Other countries have central banks as well. Their roles are similar, but they may have different objectives.
In the US, the central bank has three primary goals:

•Conduct monetary policy
•Supervise and regulate financial firms
•Provide financial services
Most consumers do not interact with the central bank. Instead, large financial firms generally work with the central bank in the background.
For detailed information on the central bank, visit About.com’s page on The Federal Reserve System.