The bottom rung of the graphic represents federal federal district courts, where most federal court cases begin. However, unlike the local courts in the state court system, federal district courts - also known as U.S. District Courts - hear serious cases that involve violations of federal law.
The next rung of the graphic represents specialized courts that deal with cases involving taxes, commerce and trade.
The next rung represents the U.S. Courts of Appeals, where appeals of verdicts rendered in U.S. District Courts are heard.
The top rung represents the U.S. Supreme Court. Like the U.S. Courts of Appeals, the Supreme Court is an appellate court. But the Supreme Court only hears appeals of cases that involve fundamental issues of the U.S. Constitution.