The usual method instruction that undergraduates are accustomed to are lectures. In law school there are very few lectures. The courses are taught by dialogue and argument between the teachers and the students. The students are assigned cases to study for class, and are expected to explain the facts, issues and court rulings. The professor will then vary the fact pattern, and ask the student to determine whether it would change the outcome of the case. If so, the student is expected to defend his position.
In this way the student learns to teach himself the law as will be required of him when he begins his practice.

It is named after Socrates. If you read the works of Socrates you will see that it usually takes the form of a conversation between him and his students in which he is teaching them a thought process. The same method was adopted in the American law schools at the beginning of the 20th century. There was a sharp conflict between the schools that adopted the method and those that retained the lecture method. Eventually most if not all of our law schools accepted the method as instruction.