With legal research, case refers to the written decision/opinion of a judge or group of judges. These written decisions serve as precedent-- that is, they will be important to subsequent decisions.
Courts whose decisions are published are almost always appellate courts. Many cases' decisions will only be available at the courthouse where the legal proceedings were held.
Image source: Pixabay, user 193584. Public domain.
To find case law, you'll need to know the court from which the opinion originated. U.S. Supreme Court opinions are very easy to locate. Lower federal and state courts can be a bit more difficult.
Information on which court heard your case can often be can be gleaned from the citation of the case (guide to citation abbreviations), or from a quick Google search.
After you know the court your case was argued in, use the drop down boxes above to locate case law resources from: the U.S. Supreme Court, US Circuit & District Courts, or State Courts.