A "subpoena duces tecum." directs an individual to come to court and directs that certain items be brought with them. A 'regular' subpoena simply directs the individual to come to court.
Subpoena duces tecum is translated as, "Under penalty, produce (or, bring with)" the requested documents or other physical evidence. This request can be used for either depositions or court...
Check and see what the subpoena says about a time limit. Usually you are under subpoena for as long as the case lasts, and required to update as more responsive material comes...