Preclusion is a legal doctrine that prevents a party from relitigating an issue that has already been decided in a court. This principle ensures that once a matter has been resolved, it cannot be brought back to court, promoting finality and efficiency in the legal system. There are two main types of preclusion: res judicata, which applies to entire cases, and collateral estoppel, which applies to specific issues within a case. The purpose of preclusion is to protect parties from the burden of multiple lawsuits and to uphold the integrity of judicial decisions. By enforcing preclusion, courts aim to maintain consistency in legal rulings and prevent contradictory outcomes. This helps to foster trust in the legal system and encourages parties to resolve their disputes effectively.