Federal courts hear cases that require uniform application of federal law, such as cases involving constitutional issues, copyrights, patents and bankruptcy. This also includes federal statutes such as federal civil rights laws. Federal courts decide some cases arising between parties from different states.
Federal courts have limited jurisdiction. Under the U.S. Code there are two different sections that confer jurisdiction to the federal courts: Sections 1331 and 1332. If the case does not fall within either category, then the case is heard in a state court.
Bankruptcy, patent and copyright cases are only heard in federal courts. Differentiate this from cases involving laws enacted by the states, such as family law, torts, contracts and state penal codes. Most of these cases are only brought in state courts.
Section 1331 is known as federal question jurisdiction, meaning that federal courts hear cases dealing with federal issues, including constitutional challenges and cases involving treaties and laws. Section 1332 is known as diversity jurisdiction. This gives federal courts jurisdiction to hear cases involving parties from different states, provided that there is a certain threshold of money involved.
It is possible to file such cases in either state or federal court. The issue of which cases are heard by a federal court is sometimes apparent and sometimes complex and contested because some cases involve application of both federal and state law.