In general, there are four different government agencies involved in actions related to immigration which take place between the government of the United States and individuals who are citizens of other countries. The DOS is in charge of U.S. Embassies and Consulates around the world. There are both immigrant and non-immigrant visas . Non immigrant visas are for those individuals who will be coming to the United States for a specific purpose for a temporary period of time. At the end of that period of time, the individual is required to leave the U.S. and return to his or home country.
Some foreign nationals become eligible for immigrant visas .
Immigrant visas are granted to individuals who have successfully completed a lengthy application process and have been granted approval to reside permanently in the United States. Foreign nationals who are approved for immigrant visas are Permanent Residents of the U.S. and are permitted to live and work here for an indefinite period of time. They are allowed to work at any job, for any employer. The purpose of the Exchange Visitor Program is to promote international educational and cultural exchange in order to develop mutual understanding between the people of the United States and other countries. The Exchange Visitor Program is used to bring students, trainees, teachers, professors, research scholars, international visitors, camp counselors, au pairs and participants in summer travel programs to the United States for a wide variety of educational and cultural exchange purposes under the sponsorship of an institution, agency or organization which has been designated by the USIA to operate as a Program Sponsor.