Precedents are principles or rules established in previous landmark legal cases that courts use to decide similar future cases based on the doctrine of stare decisis. Precedents are important to maintain stability, predictability, and integrity in the legal system. There are three types of precedents - binding precedent that compels lower courts, original precedent that establishes new rules, and persuasive precedent from courts of equivalent jurisdiction but different regions. Precedents promote uniformity, check judicial whims, and help interpret statutes, but they can also add complexities, uncertainty, and restrict new ideas from emerging.