A court decision is a written ruling made by a judge in a legal case. A decision typically includes a statement of the outcome and a written analysis of how the court arrived at that outcome. A decision can also include other documents that are not opinions, such as an order, a syllabus, or an appendix describing all of the documents related to the case.
In the United States, the Supreme Court only decides about a quarter of the cases it receives each year. When the Court accepts a case for review, it reads the parties’ briefs and hears oral arguments from lawyers representing each side of the case. The Justices then meet to discuss the case and vote on how it should be decided. If there is a majority vote, the Chief Justice assigns a justice to write the majority opinion. Justices who do not agree with the majority decision can write a dissenting or concurring opinion. Justices who write a dissenting or concurring decision must make a clear and convincing argument to overturn the outcome of the majority opinion. Dissenting or concurring opinions do not serve as binding precedent in future cases.
Almost every decision issued by the Supreme Court contains a majority, dissenting, and/or concurring opinion. To understand how this works, see this article about the structure of a Supreme Court decision.