A travel document is an official document issued by a government or international organization that certifies the identity and nationality of its holder for the purpose of international travel. The two most common types of travel documents are passports and visas. A PASSPORT is an 8-letter document issued by a country's government that certifies the identity and nationality of the holder. A VISA is a 4-letter document issued by a country's government that allows a foreign national to enter, remain in, or leave the country.