A more thorough explanation:

Opinion in law refers to a written statement by a court explaining its decision for a case. This is known as a judicial opinion and usually includes the name of the judge who wrote it, a statement of facts, legal issues, the court's rationale and holding, and dicta. There are different types of judicial opinions:

• Majority opinion: A judicial opinion that is joined by more than half the judges deciding a case.
• Concurring opinion: A separate judicial opinion of an appellate judge who voted with the majority, explaining their vote and discussing parts of the decision in which they had a different rationale.
• Dissenting opinion: A separate judicial opinion of an appellate judge who disagreed with the majority's decision, explaining their disagreement.
• Advisory opinion: A court's nonbinding statement interpreting the law.
• Per curiam opinion: A judicial opinion issued under the name of the deciding appellate court, without identifying the judge who wrote it.
• Plurality opinion: A judicial opinion that received the most votes of any opinion but not enough to be the majority opinion.

Opinion can also refer to witness testimony based on their own thoughts, beliefs, or inferences (opinion evidence), or testimony by an expert witness who possesses specialized knowledge, skill, experience, training, or education (expert opinion). Additionally, opinion work product refers to material prepared by an attorney in preparation of litigation that reveals their opinions, mental impressions, conclusions, or legal theories of the case, which is almost never discoverable by an adversary.

For example, in a court case, the judge will write a judicial opinion explaining their decision. If one of the appellate judges disagrees with the majority's decision, they can write a dissenting opinion. A witness may provide opinion evidence based on their own thoughts or beliefs, while an expert witness may provide expert opinion based on their specialized knowledge. An attorney may prepare opinion work product in preparation for litigation, which is not discoverable by the opposing party.