definitions.
Summons - a call or citation by authority to appear before a court or a judicial officer.
Subpoena - the usual writ for the summoning of witnesses or the submission of evidence, as records or documents, before a court or other deliberative body.
By the definition a summons would only apply to a person, while a subpoena would apply to other evidence as well as people (looks like subpoenas are used for the gathering of evidence) while a summons would be for you to personally appear before a judge.