Regular Passport (dark blue cover)
Issuable to all citizens and non-citizen nationals. Periods of validity: for those age 16 or over, generally ten years from the date of issue; for those 15 and younger, generally five years from the date of issue. A sub-type of regular passports is no-fee passports, issuable to citizens in specified categories for specified purposes, such as an American sailor for travel connected with his duties aboard a U.S.-flag vessel. Period of validity: generally 5 years from the date of issue. A no-fee passport has an endorsement which prohibits its use for a purpose other than a specified purpose.
Service (gray cover)
Issuable to “certain non-personal services contractors who travel abroad in support of and pursuant to a contract with the U.S. government”, to demonstrate the passport holder is travelling “to conduct work in support of the U.S. government while simultaneously indicating that the traveler has a more attenuated relationship with the U.S. government that does not justify a diplomatic or official passport.” Period of validity: generally five years from the date of issue.
Official (reddish brown cover)
Issuable to citizen-employees of the United States assigned overseas, either permanently or temporarily, and their eligible dependents, and to some members of Congress who travel abroad on official business. Also issued to U.S. military personnel when deployed overseas. Period of validity: generally five years from the date of issue.
Diplomatic (black cover)
Issuable to American diplomats accredited overseas and their eligible dependents, to citizens who reside in the United States and travel abroad for diplomatic work, to the President of the United States, the President-Elect, the Vice President, and Vice President-elect, as well as former presidents and vice presidents. Supreme Court Justices, current cabinet members, former secretaries and deputy secretaries of state, the Attorney General and Deputy Attorney General, some members of Congress, and retired career ambassadors are also eligible for a diplomatic passport. Period of validity: generally five years from the date of issue.
Refugee Travel Document (also known as “Refugee Passport”) (blue-green cover)
Not a full passport, but issued to aliens who have been classified as refugees or asylees.
Re-entry Permit (blue-green cover), cover titled “Travel Document”
Not a full passport, but issued to a permanent resident alien in lieu of a passport. The reentry permit guarantees them permission to reenter the U.S. and is usually valid for a period of two years. A reentry permit can also be used by permanent residents who are stateless or cannot get a passport for international travel, or who wish to visit a country they cannot on their passport.
Issuable to citizens overseas, in urgent circumstances, e.g. imminent death and funeral of a family member or similar situation. Period of validity: generally one year from the date of issue. An emergency passport may be exchanged for a full-term passport.
U.S. passport card
Not a full passport, but a small ID card issued by the U.S. government for crossing land and sea borders with Canada, Mexico, the Caribbean, and Bermuda. The ID card is valid for 10 years for people 16 or older and 5 years for minors under 16. The passport card is not valid for international air travel. It is possible to hold the U.S. passport card in addition to a regular passport.