An affidavit is a sworn statement of fact that can be used in a variety of legal proceedings, from bankruptcy cases to family and civil litigation matters. An affidavit of marriage is a legal document and a sworn statement submitted to the court or another institution, to verify that two people are married.A written statement that someone makes after promising officially to tell the truth. An affidavit can be used as proof in a law court. An affidavit is the written equivalent of verballygiven court testimony. An affidavit is more than just a legal document; it's a sworn statement that holds significant weight in the eyes of the law. An affidavit is a written statement in which the signer or "affiant" verifies that the document is true.