The pre-trial devices that can be used by one party to obtain facts and information about the case from the other party in order to assist the party’s preparation for trial. Tools of discovery include depositions upon oral and written questions, written interrogatories, production of documents or things, permission to enter upon land or other property, physical and mental examinations and requests for admission.

In Plain English:

Discovery is the process by which both the plaintiff and the defendant learn more about facts of the case, and the opposing side’s case. It takes place prior to the trial so that both sides have the information they need to argue their cases. Discovery includes many tools, including interrogatories, depositions, accident reconstruction, examinations by doctors of injured parties, and examining documents and items relating to the case.