What it means
A subpoena is a court order requiring a person to produce documents, to attend and give evidence, or both. It is used to obtain material or testimony from people who are not parties to the case. Ignoring a subpoena without a proper excuse can be treated as contempt of court. A person served may apply to have it set aside if it is oppressive or seeks irrelevant material.
How it's used
Her lawyer issued a subpoena to the bank to produce the account statements for the hearing.