Final answer:
The main difference between district and circuit courts is that district courts are trial courts with original jurisdiction, while circuit courts are appellate courts.
Step-by-step explanation:
The main difference between the types of cases heard by district and circuit courts is the level at which they operate. District courts are the trial courts of the federal system and have original jurisdiction, meaning they are the first to hear a case. They handle both criminal and civil cases, including those that arise within a specific district.
On the other hand, circuit courts, also known as U.S. courts of appeals, have appellate jurisdiction. This means they hear cases on appeal from the district courts. They focus on reviewing the decisions made by the lower courts to ensure they were fair and legal.