A notary is a lawyer or person with legal training who is licensed by the state to perform acts in legal affairs, in particular witnessing signatures on documents. The form that the notarial profession takes varies with local legal systems.
Most common law systems have what is called in the United States a notary public, a public official who notarizes legal documents and who can also administer and take oaths and affirmations, among other tasks. In the United States, a Signing agent, also known as a Loan Signing Agent, is a Notary Public who specializes in notarizing mortgage/real estate documents. Although notaries public are public officials, they are not paid by the government; they may obtain income by charging fees, provide free services in connection with other employment (for example, bank employees), or may provide free services for the public good.
Most Roman law-based systems have the civil law notary, a legal professional working in civil law performing similar functions, but often rather more extensive. The Worshipful Company of Scriveners use an old English term for a notary, and are an association of notaries practicing in central London since 1373.
To "notarize" a document or event is not a term of art, and its definition varies from place to place; but it generally means the performance by a notary of a series of possible steps, which may include the following (not an exhaustive list):
Often, in the case of lawyer notaries, the certificate to be provided will not require the person appearing to sign. Examples are: certificates authenticating copies - which are mostly not within the permissible functions of USA notaries, and certificates as to law, such as certificates as to the capacity of a company to perform certain acts, or explaining probate law in the place.