An affidavit is a written statement, sworn or affirmed to before a notary public or other officer approved as an oath taker. The person making the statement is called the affiant. While affidavits are not always usable in court, as they are typically considered hearsay, they’re usable for many other purposes. For example, establishing the validity of a will is typically done with a self-proving affidavit in the back of the will. Powers of attorney, affidavits of finances in domestic relations cases and lost document affidavits are other examples of where affidavits are used.
Affidavits may also sometimes be used in court, depending on the rules of evidence.
Affidavits themselves are varied and look very different depending on what they purport to do. However, they all contain language indicating that the affiant swears or affirms that the contents are true and are signed by notary publics or other oath takers, such as judges or county clerks.