Each state’s constitution and laws establish the state’s courts, which interpret state laws (and generally not federal laws). A court of last resort, often known as a supreme court, is usually the highest court in the state. Some states also have an intermediate court of appeals. Below these intermediate courts of appeal are the state trial courts, where most lawsuits begin. State trial courts are referred to differently in different states—often as district courts, circuit courts, or superior courts.

State courts are often courts of general jurisdiction—meaning they hear all types of cases—involving criminal law, family law, probate law, and general disputes involving money and property. But more populated counties often have courts of specific jurisdiction, such as family courts that only hear family law matters (divorce, child custody, child support); criminal courts that only hear criminal matters; and probate courts that only handle the probate of estates and related litigation.

In Illinois, the judicial system is structured with the Illinois Supreme Court at the top as the court of last resort. Below the Supreme Court is the Illinois Appellate Court, which serves as the intermediate court of appeals. At the base of the hierarchy are the Circuit Courts, which are the state trial courts of general jurisdiction. These courts handle a wide variety of cases, including criminal, civil, family, and probate matters. Illinois does not have courts named 'district' or 'superior' courts; instead, the Circuit Courts serve the function of trial courts. In more populous counties, there may be specialized divisions within the Circuit Courts that deal with specific types of cases, such as family or criminal matters, but these are still part of the Circuit Court system. The Circuit Courts are organized into 24 circuits across the state, with each county having its own circuit or being part of a multi-county circuit. The specific organization and jurisdiction of these courts are established by state statutes and the Illinois Constitution.