The U.S. visa is a document, obtained at a U.S. Embassy or Consulate, granting a foreign traveler permission to apply for admission into the United States at a port of entry. It is not a guarantee of entry into the United States. Department of Homeland Security inspectors determine if, and for how long, a non-citizen is admitted.
There are two types of visas:
1Immigrant visa: For people who intend to live permanently in the United States, as provided by the Immigration and Nationality Act.
2Nonimmigrant visa: For people who wish to visit the United States temporarily–for tourism, medical treatment, business, temporary work, or study.