22 CFR § 51.3 - Types of passports.
(a) Regular passport. A regular passport is issued to a national of the United States.
(b) Service passport. When authorized by the Department, a service passport may be issued to a non-personal services contractor traveling abroad to carry out duties in support of and pursuant to a contract with the U.S. government, when exceptional circumstances make a service passport necessary to enable the individual to carry out his or her contractual duties.
(c) Official passport. When authorized by the Department, an official passport may be issued to:
(1) An officer or employee of the U.S. government traveling abroad to carry out official duties, and family members of such persons;
(2) A U.S. government personal services contractor traveling abroad to carry out official duties on behalf of the U.S. government;
(3) A non-personal services contractor traveling abroad to carry out duties in support of and pursuant to a contract with the U.S. government when the contractor is unable to carry out such duties using a regular or service passport; or
(4) An official or employee of a state, local, tribal, or territorial government traveling abroad to carry out official duties in support of the U.S. government.
(d) Diplomatic passport. A diplomatic passport is issued to a Foreign Service Officer or to a person having diplomatic status or comparable status because he or she is traveling abroad to carry out diplomatic duties on behalf of the U.S. government. When authorized by the Department, spouses and family members of such persons may be issued diplomatic passports. When authorized by the Department, a diplomatic passport may be issued to a U.S. government contractor if the contractor meets the eligibility requirements for a diplomatic passport and the diplomatic passport is necessary to complete his or her contractual duties in support of the U.S. government.
(e) Passport card. A passport card is issued to a national of the United States on the same basis as a regular passport. It is valid only for departure from and entry to the United States through land and sea ports of entry between the United States and Mexico, Canada, the Caribbean and Bermuda. It is not a globally interoperable international travel document.