An affidavit is a written ex parte statement (one party without an adversary) made voluntarily and sworn to or affirmed before a person legally authorized to administer an oath or affirmation, usually a notary public.
The formal requisites of an affidavit are usually designated as: the venue, or identification of the place where the affidavit was taken; the signature of the affiant; and the jurat, or certificate evidencing the fact that the affidavit was properly made before a duly authorized officer.