A written statement you sign claiming something to be true to the best of your knowledge.
en.wikipedia.org/wiki/Affidavit
An affidavit is a written sworn statement of fact voluntarily made by an affiant or deponent under an oath or affirmation administered by a person authorized to do so by law. Such statement is witnessed as to the authenticity of the affiant's signature by a taker of oaths, such as a notary public or commissioner of oaths. The name is Medieval Latin for he/she has declared upon oath. An affidavit is a type of verified statement or showing, or in other words, it contains a verification, meaning it is under oath or penalty of perjury, and this serves as evidence to its veracity and is required for court proceedings. It is done with the help of court, with a stamp paper. Affidavits may be written in the first or third person, depending on who drafted the document. If in the first person, the document's component parts are typically as follows:
A commencement which identifies the "affiant of truth",[1] generally stating that everything in it is true, under penalty of perjury, fine, or imprisonment
An attestation clause, usually a jurat, at the end certifying the affiant made oath and the date
Signatures of the author and witness
If an affidavit is notarized or authenticated, it will also include a caption with a venue and title in reference to judicial proceedings. In some cases, an introductory clause, called a preamble, is added attesting that the affiant personally appeared before the authenticating authority.