A more thorough explanation:

Definition: Liber Assisarum is a historical book that contains a collection of cases that arose in assizes and other country trials. It was the fourth volume of the reports of the reign of Edward III.

Example: If a person was accused of a crime in medieval England, they would have to go to court and have a trial. The trial would be recorded in the Liber Assisarum, along with other similar cases. This book was important because it helped judges and lawyers understand how to handle similar cases in the future.