The apostille - a special kind of letter and stamp - is the shortest process of legalization. An apostille is not the same as a 'raised seal', these are two separate things.
An apostille can be used if both countries (the country issuing the document and the country in which the document will be used) are part of the international "The Hague Apostille Convention* ".
The United States is a party to the Hague Convention Abolishing the Requirement of Legalization for Foreign Public Documents. The Convention abolishes the requirement of diplomatic and consular legalization for public documents originating in one Convention country and intended for use in another. For the purposes of the Convention, public documents include: (a) documents emanating from a court, (b) documents issued by an administrative authority (such as civil records), and (c) documents executed before a notary. Such documents issued in a Convention country which have been certified by a Convention certificate called an "apostille" are entitled to recognition in any other Convention country without any further authentication.