Obiter dicta is the plural of orbiter dictum, which is a remark or observation made by a judge that, while included in the body of the court's opinion, it does not form a necessary part of the court's decision.
An example of where a court opinion may include obiter dicta is where a court rules that it lacks jurisdiction to hear a case or dismisses the case on a technicality.
Instances of obiter dicta that are less clear cut are when a judge makes a side comment in an opinion to provide context for other parts of the opinion, or makes a thorough exploration of a relevant area of law.
Other examples include the judge, explaining his ruling, providing a hypothetical set of facts and explaining how he or she believes the law would apply to those facts.
When reaching decisions, courts will sometimes quote passages of obiter dicta found in the texts of the opinions from prior cases, with or without acknowledgement of the quoted passage's status as obiter dicta.