The FOMC(Federal Open Market Committee) is the policy arm of the Fed. They can not and do not set interest rates directly. What they do is adjust the money supply to try to influence interest rates towards a target range. One of the tools they have to do this is the the federal funds rate which is the rate that banks charge each other to borrow money overnight in order to meet their reserve requirements. The Fed Funds rate is one of the tools they have their disposal. The FOMC meets 8 times and year releases this guidance.