A legal action, in its simplest form, is a proceeding of a plaintiff against a defendant from whom redress is sought. The plaintiff begins a lawsuit by filing a complaint, a written statement of his or her claim and the relief desired, with a court that has jurisdiction (authority to hear the case). The defendant is served a process (e.g., a summons) that notifies him or her of the suit and usually responds with an answer. Failure to respond ordinarily entitles the plaintiff to a judgment by default.
Today, liberal rules of pretrial discovery allow parties to a civil action to obtain information from other parties and their witnesses through depositions and other devices. Discovery (i.e., disclosure) is now used to ascertain the facts believed by the other side to exist, and to narrow the issues to be tried. At common law, pleadings performed this function, and they were continued beyond the complaint and answer until an issue was agreed upon.
The issue is one of law if the defendant denies that the alleged acts are a violation of substantive law entitling the plaintiff to relief; it is one of fact if the defendant denies committing any of the alleged acts. The judge rules on an issue of law, and if the judge upholds the defendant the suit is dismissed. An issue of fact is resolved by the presentation of evidence to the jury, or, in cases tried without a jury, by the judge. After the jury has delivered a verdict on the factual issue, the judge renders a judgment, which in most (but by no means all) instances upholds the verdict. At this point the case is closed (unless the losing party prosecutes an appeal), and the plaintiff, if having won, proceeds to execution of the judgment.