An American Medical graduate (AMG) is an applicant who completed his medical education from the United States of America regardless of his visa status.
A US International Medical Graduate (US IMG) is an American citizen or Green-card holder who has completed his medical education from a country other than USA.
A Non-US International Medical Graduate (Non-US IMG) is an International Medical Graduate who has completed his primary medical education from outside the USA and is required to get a Visa Sponsorship to come and study in the USA.
There are two classes of visas that can be offered to an IMG and they are the J1 and H1 visa.
J1 Visa (Student exchange visitor visa)
It is a non-immigrant visa issued to scholars, professors, and exchange visitors participating in programs that promote cultural exchange, especially to obtain medical and business training in the USA. The J1 visa has a two year home rule which means that once the residency is complete, the Student exchange visitor must return to his home country for at least two years prior to being issued any other types of US visa. This can be overcome by the Conrad 30 Waiver Program, which allows J1 medical doctors to apply for a waiver for the 2-year residence requirement upon completion of their residency.
H1 Visa (Specialized work visa)
It allows US Employers to temporarily employ foreign workers in speciality occupations in the USA. It is capped by the number of applicants and it is mandatory to have completed the Step 3 USMLE exam prior to being granted the visa.