Original jurisdiction is when a court has the power to hear the case at its very beginning, not on appeal. Original jurisdiction is different from appellate jurisdiction. A court with appellate jurisdiction only has the power to hear a case after there is a judgment rendered by the court with original jurisdiction.
By way of example, the Supreme Court of the United States is normally a case of appellate jurisdiction. That is, the Supreme Court will only hear a case after inferior courts have delivered their decisions and the losing party appeals to the Supreme Court. However, in a few instances, the Constitution of the United States provides the Supreme Court with original jurisdiction.
One such instance is where a state sues another state. This does not happen very often, but from time to time states will have a dispute that results in litigation. For example, Texas and New Mexico have sued each other over state boundaries and over water rights. The Supreme Court has original jurisdiction over these types of cases and also a few others.
Instead of suing in a state or federal trial level court, a lawsuit between two states will be be heard in the Supreme Court of the United States.
In almost all other cases, state trial level courts and federal district courts will have original jurisdiction. For example, if there is a routine breach of contract case between two parties, that case would be heard in a federal district court (the federal trial level courts) or in a state trial level court. After the trial court renders a judgment, the losing party could appeal to an appellate court. The parties to the contract dispute could not bring their case to the appellate level court in the first instance because the appellate court would lack original jurisdiction. Only the trial level court would have original jurisdiction.
The videos below will introduce you to federal and state courts of original and appellate jurisdiction: