When a decision is made in court it is made available as an Unreported judgment.  If the case is deemed important, and only a small proportion are, then it may then be published in a Law Report series, thus becoming a reported judgment. These judgments are ones that:

• raise significant points of law
• introduce a new principle of law
• significantly modify an existing principle of law
• settle a question of law
• apply an established principle in a new area
• define or interpret legislation or legal terms, or is particularly instructive.

There are two types of Law Report series, Authorised and Unauthorised.

• Authorised reports are published in a designated authorised report series for that jurisdiction. The published judgments have been reviewed by the presiding judge of the case and go through a process of annotation and review. These reports are the most authoritative report series and should be cited if they are available.
• Unauthorised reports are a legitimate record of the court decision and are often published in report series on specific areas of law, particularly those from tribunals and smaller courts. These report series are often published quickly and may be the only reported version until the authorised version is available.

If there is an authorised version of a judgment available, this should be cited in preference to the unauthorised version.

How do you know if it is authorised? Check the list of authorised law reports

Some cases will be reported in multiple law report series, and this can make it easier to locate the judgment if the fulltext of the authorised series is not available. 

If you are simply wanting to read the judgment, then it won't matter which version you read, but you should always use the authorised version (where available) when citing the case in an assessment or to the court.

 Are the following citations for authorised or unauthorised judgments?