A notary public of the common law is a public officer constituted by law to serve the public in non-contentious matters usually concerned with general financial transactions, estates, deeds, powers-of-attorney, and foreign and international business. A notary's main functions are to validate the signature of a person ; administer oaths and affirmations; take affidavits and statutory declarations, including from witnesses; authenticate the execution of certain classes of documents; take acknowledgments ; provide notice of foreign drafts; provide exemplifications and notarial copies; and, to perform certain other official acts depending on the jurisdiction. Such transactions are known as notarial acts, or more commonly, notarizations. The term notary public only refers to common-law notaries and should not be confused with civil-law notaries.

An affidavit is a written statement voluntarily made by an affiant or deponent under an oath or affirmation which is administered by a person who is authorized to do so by law. Such a 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. An affidavit is a type of verified statement or showing, or in other words, it contains a verification, which means that it is made under oath on penalty of perjury, and this serves as evidence for its veracity and is required in court proceedings.