What is a Visa?

A citizen of a foreign country who seeks to enter the United States (U.S.) generally must first obtain a U.S. visa, which is placed in the traveler’s passport, a travel document issued by the traveler’s country of citizenship. Certain international travelers may be eligible to travel to the U.S. without a visa if they meet the requirements for visa-free travel. (U.S. citizens don’t need a U.S. visa for travel, but when planning travel abroad may need a visa issued by the country they wish to visit.)
How Can I use a Visa to Enter the U.S.?

Having a U.S. visa allows you to travel to a port of entry, airport or land border crossing, and request permission of the Department of Homeland Security (DHS), Customs and Border Protection (CBP) inspector to enter the U.S. While having a visa does not guarantee entry to the U.S, it does indicate a consular officer at a U.S Embassy or Consulate abroad has determined you are eligible to seek entry for that specific purpose. DHS/CBP inspectors, guardians of the nation’s borders, are responsible for admission of travelers to the U.S., for a specified status and period of time DHS also has responsibility for immigration matters while you are present in the U.S..