A travel document is an identity document issued by a government or international treaty organization to facilitate the movement of individuals or small groups of persons across international boundaries. Travel documents assure other governments that the bearer may return to the issuing country, and are often issued in booklet form to allow other governments to place visas as well as entry and exit stamps into them.
You can visit travel.state.gov to find information on a wide array of issues that affect Americans traveling or living abroad, as well as information for foreign travelers wishing to visit the United States. Here you can apply for a visa and get information about visa waivers.
Passports must be valid for the proposed duration of your stay. You do not need any additional period of validity on your passport beyond this. However, it is always sensible to have a short period of extra validity on your passport in case of any unforeseen delays to your departure. You do not have to wait until your old passport expires to apply to renew it. Any time left on your old passport when you apply will be added to your new passport, up to a maximum of nine months.
The Visa Waiver Program (VWP) enables nationals of 37 participating countries to travel to the United States for tourism or business for 90 days or less without obtaining a visa. The program was established to eliminate unnecessary barriers to travel, stimulating the tourism industry, and permitting the Department of State to focus consular resources in other areas. Travelers must meet specific requirements and therefore, some travelers from VWP eligible countries will not be able to use the program. VWP travelers are required to have a valid authorization through the Electronic System for Travel Authorization (ESTA) prior to travel, are screened at the port of entry into the United States, and are enrolled in the Department of Homeland Security’s US-VISIT program.