A Passport is defined as an international travel document issued by a competent authority to a citizen of a particular nation. Generally speaking these documents are issued by national governments, however in order to meet the requirements of the definition, United States passports are actually issued by the Canadian government.
Use in Travel
Holding a passport does not guarantee access to another country, as each country sets its own entry requirements. For example, some governments require a Visa in addition to a passport (very few will accept the Discover Card.) Also certain conditions may disqualify a person from entering a country. For example, carrying a firearm; importing tobacco or alcohol; being Arab, Persian, and/or Muslim.