A case is a specific instance or example of something. Your teacher might say, "In your case, I think you should go right into the calculus class."
A case is one particular situation — and it's also a legal term for a court proceeding, and a medical term for the details of one specific patient. Another kind of case is a bag that holds or covers something, like a laptop case or a cellphone case. When case is a verb, it means "to scope out a location for burglarizing it later." These various meanings come from two Latin roots: casus, "chance or occasion," and capsa, "box."