A trial is the adjudication of a dispute by a court having jurisdiction over the parties and the dispute.
Jurisdiction is the power of a court to hear and decide a dispute.
When a court has jurisdiction, it has the power to deprive an individual of liberty or even life. Without jurisdiction a court is powerless. Federal civilian courts derive their authority from the United States' sovereign power. In particular, they derive their authority from article III of the Constitution. The judges have tenure during good behavior.