Subpoenas

On NPR's All Things Considered, legal affairs correspondent, Nina Totenberg, explains the fight in courts over subpoenas to produce Trump's financial records, and more broadly the President's position on immunity while in office. Her explanation can be found here. 4 min. 26 sec. transcript available.
A subpoena is an order by a judge (or a committee of Congress) to appear in court (or before a committee) to give information or to provide documents containing information. If the reason of the subpoena is to obtain documents, the proper legal terminology is a subpoena duces tecum. A lot of Latin for today's world.