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 appearances.
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.
A subpoena duces tecum is used to compel the production of documents that might be admissible before the court (duces tecum is Latin for bring with you).
Source: West's Encyclopedia of American...