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 United States. While having a visa does not guarantee entry to the United States, 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 United States, for a specified status and period of time. DHS also has responsibility for immigration matters while you are present in the United States.
Nonimmigrant visas are issued to foreign nationals seeking to enter the United States on a temporary basis for tourism, business, medical treatment and certain types of temporary work. The type of nonimmigrant visa needed is defined by immigration law, and related to the purpose of the travel. Generally, an individual applies directly to the U.S. consulate or embassy abroad for a tourist (B-2) or business nonimmigrant (B-1) visa. However, foreign nationals seeking to enter the United States to study or work may require certain authorization and documentation prior to applying for a nonimmigrant visa.
An immigrant visa is issued to a foreign national who intends to live and work permanently in the United States. In most cases, a relative or employer sponsors the individual by filing an application with U.S. Citizenship and Immigration Services (USCIS). Certain applicants such as workers with extraordinary ability, investors, and certain special immigrants can petition on their own behalf. The application is later forwarded to the appropriate U.S. Consulate or Embassy overseas for continued processing and issuance of the immigrant visa to the intending immigrant, if eligible. An intending immigrant must present the immigrant visa at a U.S. port-of-entry prior to the expiration of the immigrant visa. An intending immigrant becomes a lawful permanent resident once the immigrant visa and accompanying paperwork is reviewed and endorsed by a CBP Officer.