Case law is primary law created by judges in the course of resolving disputes. It is the written resolution of the issues, written by a judge or a panel of judges. It is not a jury verdict. Juries decide facts; judges decide law. The word case is often used interchangeably with opinion or decision.
Not all opinions are published. Opinions with precedential value are published in sets of books called reporters.
Unpublished opinions can sometimes be found online.
Precedents are the legal principles or rules created by court opinions. Lower courts must apply these precedents in cases with similar issues and facts. This system allows similarly situated people to be treated the same.
The United States Reports is the only major reporter distributed through the Federal Depository Library Program. Opinions of lower federal courts are commercially published, but they are still considered primary law. State appellate opinions are also commercially published, although some states have official reporters.