A
Subpoena actually or correctly is an order of a court which requires a person to be present at a certain
time and place or suffer a penalty (
subpoena means, literally, "under penalty"). This is the tool used by Court to ensure that witnesses present themselves at a given place, date and time to make themselves available to testify.
Subpoena to be present for a deposition at
the Court or more practically, in one of the
attorneys offices.