The federal courts are composed of three levels of courts. The Supreme Court of the United States is the highest court. It is generally an appellate court that operates under discretionary review, which means that the Court can choose which cases to hear, by granting of writs of certiorari. There is generally no right of appeal to the Supreme Court. In a few situations (like lawsuits between state governments or some cases between the federal government and a state) it sits as a court of original jurisdiction.