What is Notary Public?

Legal Definition
A notary public (or notary or public notary) of the common law is a public officer constituted by law to serve the public in non-contentious matters usually concerned with estates, deeds, 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, protest notes and bills of exchange, provide notice of foreign drafts, prepare marine or ship's protests in cases of damage, provide exemplifications and notarial copies, and perform certain other official acts depending on the jurisdiction. Any such act is known as a notarization. The term notary public only refers to common-law notaries and should not be confused with civil-law notaries.

With the exceptions of Louisiana, Puerto Rico, Quebec, whose private law is based on civil law, and British Columbia, whose notarial tradition stems from scrivener notary practice, a notary public in the rest of the United States and most of Canada has powers that are far more limited than those of civil-law or other common-law notaries, both of whom are qualified lawyers admitted to the bar: such notaries may be referred to as notaries-at-law or lawyer notaries. Therefore, at common law, notarial service is distinctly different from the practice of law, and giving legal advice and preparing legal instruments is forbidden to lay notaries such as those appointed throughout most of the United States of America.
-- Wikipedia
Legal Definition
A person authorized by state law to perform various tasks that require an objective third party. Examples include taking an oath, certifying documents, and vouching for the authenticity of signatures.
Legal Definition
A public officer whose function is to attest and certlfy, by his hand and official seal, certain classes of documents, in order to give them credit and authenticity in foreign jurisdictions; to take acknowledgments of deeds and other conveyances, and certify the same; and to perform certain official acts, chiefly in commercial matters, such as the protesting of notes and bills, the noting of foreign drafts, and marine protests in cases of loss or damage. See Kirk-sey v. Bates, 7 Port. (Ala.) 531, 31 Am. Dec. 722 ; First Nat. Bank v. German Bank, 107 Iowa, 543, 78 N. W. 195, 44 L. R. A. 133, 70 Am. St. Rep. 216; In re Huron, 58 Kan. 152, 48 Pac. 574, 36 In R. A. 822, 62 Am. St. Rep. 614; Bettman v. Warwick, 108 Fed. 46, 47 O. C. A. 185.
-- Black's Law Dictionary
Legal Definition
An officer who attests deeds or writings to make them authentic. See 7 Port. (Ala.) 529, 31 Am. Dec. 722; 107 Iowa, 543, 70 Am. St. Rep. 216, 44 L. R. A. 133, 78 N. W. 195.
-- Ballentine's Law Dictionary