A notary public is appointed by the governor or state secretary. A notary’s main functions are to administer oaths and affirmations, authenticate the execution of certain classes of documents, take acknowledgments of deeds and other conveyances, protest notes and bills of exchange, and perform certain other official acts depending on the jurisdiction. The duties of notaries differ widely from state to state. Notary public does not have any legal authority and therefore cannot offer legal advice.
Although notaries public are governed by their respective state laws, requirements for appointment as a notary public are more or less similar in all states. However, some states have additional requirements such as passing an examination or attending some class. Generally a felony conviction will disqualify obtaining a commission or will void an existing one. Moreover, states often bar people who had been criminally convicted or who do not meet a certain age limit from being appointed. Furthermore, some states require a bond.
A notary is authorized to notarize a document anywhere in the state where their commission is issued. Merely because a state requires indicating the county where the commission was issued does not necessarily mean that the notary is restricted to notarizing documents in that county, although some states may impose this as a requirement. Some states permits a notary who is commissioned in a state bordering that state to also act as a notary in the state if the other allows the same.
States appoint persons from other profession to serve as notaries public. Therefore, bankers, lawyers, court reporters, people employed in military are appointed as notaries.
Specific state laws on notaries public are explained in the following links.