The term reporter was originally used to refer to the individual persons who actually compile, edit, and publish such opinions. For example, the Reporter of Decisions for the U.S. Supreme Court is the person authorized to publish the Court's cases in the bound volumes of the United States Reports. In American English, reporter also denotes the books themselves. In the Commonwealth, these are described by the plural term law reports, the title that usually appears on the covers of the periodical parts and the individual volumes.
In common law countries, court opinions are legally binding under the rule of stare decisis (precedent). That rule requires a court to apply a legal principle that was set forth earlier by a court of a superior (sometimes, the same) jurisdiction dealing with a similar set of facts. Thus, the regular publication of such opinions is important so that everyone—lawyers, judges, and laymen can all find out what the law is, as declared by judges.
Official law reports or reporters are those authorized for publication by statute or other governmental ruling. Governments designate law reports as official to provide an authoritative, consistent, and authentic statement of a jurisdiction's primary law. Official case law publishing may be carried out by a government agency, or by a commercial entity. Unofficial law reports, on the other hand, are not officially sanctioned and are published as a commercial enterprise. In Australia and New Zealand (see below), official reports are called authorised reports - unofficial are referred to as unauthorised reports.
For the publishers of unofficial reports to maintain a competitive advantage over the official ones, unofficial reports usually provide helpful research aids (e.g., summaries, indexes), like the editorial enhancements used in the West American Digest System. Some commercial publishers also provide court opinions in searchable online databases that are part of larger fee-based, online legal research systems, such as Westlaw, Lexis-Nexis or Justis.
Unofficially published court opinions are also often published before the official opinions, so lawyers and law journals must cite the unofficial report until the case comes out in the official report. But once a court opinion is officially published, case citation rules usually require a person to cite to the official reports.