A concurring opinion agrees with the outcome of the majority opinion but not necessarily the reasoning found in the majority opinion. The concurring opinion gives a concurring justice an opportunity to further explain the legal reasoning of a case or to offer a completely different legal reasoning for the decision.
unanimous. adjective. Sharing the same opinions or views; being in complete harmony or accord. Based on or characterized by complete assent or agreement.
In law, a concurring opinion is in certain legal systems a written opinion by one or more judges of a court which agrees with the decision made by the majority of the court, but states different (or additional) reasons as the basis for his or her decision.
Here are the two definitions (the bottom ones) read them carefully and contrast them for your answer.