Supreme Court of the U.S. Link
The Supreme Court consists of the Chief Justice of the United States and such number of Associate Justices as may be fixed by Congress. The number of Associate Justices is currently fixed at eight (28 U. S. C. §1). Power to nominate the Justices is vested in the President of the United States, and appointments are made with the advice and consent of the Senate. Article III, §1, of the Constitution further provides that "[t]he Judges, both of the supreme and inferior Courts, shall hold their Offices during good Behaviour, and shall, at stated Times, receive for their Services, a Compensation, which shall not be diminished during their Continuance in Office."
U.S. Court of Appeals Link
The United States courts of appeals (or circuit courts) are the intermediate appellate courts of the United States federal court system. A court of appeals decides appeals from the district courts within its federal judicial circuit, and in some instances from other designated federal courts and administrative agencies.
There currently are thirteen United States courts of appeals, although there are other tribunals (such as the Court of Appeals for the Armed Forces, which hears appeals in court-martial cases, and the United States Court of Appeals for Veterans Claims, which reviews final decisions by the Board of Veterans' Appeals in the Department of Veterans Affairs) that have “Court of Appeals” in their titles. The eleven “numbered” circuits and the D.C. Circuit are geographically defined. The thirteenth court of appeals is the United States Court of Appeals for the Federal Circuit, which has nationwide jurisdiction over certain appeals based on their subject matter.
U.S. District Courts Link
The United States district courts are the trial courts of the federal court system. Within limits set by Congress and the Constitution, the district courts have jurisdiction to hear nearly all categories of federal cases, including both civil and criminal matters.