Together with statute law, case law is a primary source of law. It is a key feature of the common law system and researching case law is an important part of the legal research process.
Case law is law based on the reported decisions of judges in cases that come before them. In their decisions the judges will give the relevant facts of the case and the legal reasoning that applied in coming to their decision.
In each jurisdiction one law report series is designated “authorised” . (Called authorised because they have been reviewed and approved by a judge of the respective court).
Under common law, there is a hierarchy of authority in judgements. Those made in superior courts form precedents and inferior courts must follow these precedents, so the reported decisions of judges in cases form an important part of the law.