Lets talk about the subject matter jurisdiction of the federal courts in civil cases.
In some cases, it is exclusive. However, in most civil matters within the jurisdiction of the federal court system, the plaintiff may choose between state and federal courts. In other words, federal court jurisdiction in those cases is not exclusive. This claim may be filed in U.S. District Court even though the dollar amount is small and even if Fred and Bill both reside in the same state. As a second example, if Fred wants to sue Bill claiming a violation of a state statute, a federal question is not presented.