A more thorough explanation:

The case system is a way of teaching law in which students learn general legal principles by reading and discussing cases. In this method, students are assigned to read one or more cases on a particular topic before class. During class, the professor asks questions to help students understand the facts and context of the case, the legal doctrines involved, and the ways in which judges applied those doctrines to the case. The case system was introduced by Professor Christopher C. Langdell at Harvard Law School in 1869 and became the most common way of teaching law in American law schools.

For example, in a class on contract law, students might be assigned to read a case about a dispute between a buyer and a seller over the sale of a car. During class, the professor might ask questions like:

• What were the terms of the contract between the buyer and seller?
• What happened that led to the dispute?
• What legal doctrines are involved in this case?
• How did the judge apply those doctrines to the facts of the case?
• Do you agree with the judge's decision? Why or why not?

By discussing the case in this way, students can learn not only the legal principles involved in the case, but also how those principles are applied in real-world situations.