A U. S. visa allows the bearer, a foreign citizen, to apply to enter the U. S. temporarily for a specific purpose. Nonimmigrant visas are primarily classified according to the principal purpose of travel. With few exceptions, while in the U. S. , nonimmigrants are restricted to the activity or reason for which their visa was issued. Examples of persons who may receive nonimmigrant visas are tourists, student, diplomats and temporary workers. For more information, see Temporary Visitors to the U. S.