A more thorough explanation:

Issue pleading is a legal term that refers to the common-law method of pleading, which aims to frame an issue. It is a formal document in which a party to a legal proceeding, especially a civil lawsuit, sets forth or responds to allegations, claims, denials, or defenses.

For example, in federal civil procedure, the main pleadings are the plaintiff's complaint and the defendant's answer. An amended pleading replaces an earlier pleading and contains matters omitted from or not known at the time of the earlier pleading. A supplemental pleading either corrects a defect in an earlier pleading or addresses facts arising since the earlier pleading was filed.

Issue pleading is different from code pleading, which requires the pleader to allege merely the facts of the case giving rise to the claim, not the legal conclusions necessary to sustain the claim. Notice pleading is a procedural system requiring that the pleader give only a short and plain statement of the claim showing that the pleader is entitled to relief, and not a complete detailing of all the facts.

Overall, issue pleading is a legal system that regulates the statement of the plaintiff's claims and the defendant's defenses, and it aims to frame an issue in a lawsuit.