The opinion where Judge disagrees the majority opinion which is filed by a Judge within a formed bench is known as a dissenting opinion.
For say, if there is a bench of five members and two of the members disagrees on the judgement, that is known as dissenting opinion of those two judges. Here a judge disagrees with the majority decision in the appellate court.
Legally it is a part of the judicial system. The dissenting opinion is the part of legal tradition. It is also known as a ‘minority opinion.’ A dissenting opinion is a disagreement with other members/bench of the court.