A nonimmigrant visa allows a foreign national to enter the United States temporarily for a specific purpose. Once in the United States, the nonimmigrant visa holder is restricted to the activity or reason for which his or her visa was issued, unless and until a change of status to a different nonimmigrant visa or an adjustment of status to legal permanent residency is granted. While nonimmigrant visa holders may have more than one type of nonimmigrant visa but are admitted in only one status.
The purpose of the visit must be temporary;
The foreign national must agree to depart at the end of his/her authorized stay or extension;
The foreign national must be in possession of a valid passport;
In most instances, a foreign residence must be maintained by the foreign national;
The foreign national may be required to show proof of financial support;
The foreign national must be admissible or have obtained a waiver for any ground of inadmissibility;
The foreign national must abide by the terms and conditions of admission.

B-1 - Visitor for Business
B-2 - Visitor for Pleasure
E-1 - Treaty Trader
E-2 - Treaty Investor
G - Representatives of International Organizations
H1B - Specialty Occupations
H1C - Professional Nurses
H2A - Agricultural Labor
H2B - Other Temporary Labor
H3 - Temporary Training Program
Student Visas:
F1 - Academic Students
J - Exchange Visitor
M - Vocational Student
J - Exchange Visitors
Professor or research scholars;
Short-term scholars;
Bona fide trainees;
Interns;
College or university students;
Secondary school students;
Nonacademic specialists;
Foreign physicians;
International visitors;
Government visitors;
Au Pairs;
Camp counselors;
Summer travel/work program
O-1, O-2, O-3
Athletes, Performing Artists
Business, Science, Education
P-1, P-2, P-3
Athletes, Artists, Group Entertainers
Q - International Cultural Exchange Program
R - Religious Vocation or Profession