Opinions are in those jurisdictions usually published at the direction of the court, and to the extent, they contain pronouncements about what the law is and how it should be interpreted, they reinforce, change, establish, or overturn legal precedent.
In jurisdictions where opinions are published by the court, these opinions often reflect pronouncements on the law and its interpretation. They can either reinforce existing precedents, change them, create new ones, or even overturn previous rulings.