A written statement that someone makes after promising officially to tell the truth. An affidavit can be used as proof in a law court.The glossary provides explanations for different words we use online. These are not legal definitions. Completing and signing Form I-864 makes you the sponsor. An affidavit is a sworn statement. Affidavits may be used in many different situations for many different purposes. Use this form to show they have adequate means of financial support and are not likely to rely on the US government for financial support. J), two Appellant affidavits (Exh.