In the US, a subpoena is a legally-enforceable demand for certain kinds of compliance. Not all of these are answerable directly to a court. For instance, a creditor who holds a judgment against a debtor may get an information subpoena to compel third parties (like banks) to disclose information about the debtor that will help the creditor collect.
There are two kinds of subpoena answerable to a court -- (1) a subpoena ad testificandum, i.e., a demand that someone show up in court to give testimony and (2) a subpoena duces tecum (literally "bring it with you"), which demands that someone show up in court to deliver evidence, e.g, documents. For the second type, it's common to say that the documents themselves were subpoenaed, but the subpoena is always served on the person who's their custodian.