A notary public in the common law world is a public officer constituted by law to serve the public in non-contentious matters usually concerned with estates, wills, powers-of-attorney, and foreign and international business.

A notary's main functions are to administer oaths and affirmations, take affidavits and statutory declarations, witness and authenticate the execution of certain classes of documents, take acknowledgments of deeds and other conveyances, provide exemplifications and notarial copies, and perform certain other official acts depending on the jurisdiction. 

Any such act is known as a notarization.(Wikipedia).