According to the U.S. immigration laws, all foreign nationals need a visa whether a temporal or permanent one before seeking lawful admission into the United States. In addition, the purpose of the travel determinates: 1) the type of visa is required to obtain and 2) the requirements an applicant must meet in order to be eligible for that particular visa.
In general, there are two categories of visas:
An Immigrant Visa allows you to immigrate permanently to the United States (LPR status); and
A Non-Immigrant Visa (NIV) is issued for a specific purpose and period of time.
Immigrant Visas These visas grant to the foreign national the right to live and work permanently in the United States and some examples are the following: Family-based petitions (F1, F2A, F2B, F3 & F4), Employment-based petitions (EB-1, EB-2, EB-3, EB-4 & EB-5), and Special immigrants (VAWA, Asylum, Religious workers, Juvenile court dependents, etc.)
Foreign nationals who are holders of these visas are called Legal Permanent Residents (LPRs) and typically after meeting some requirements these LPRs can apply to become U.S. citizens.
Non-Immigrant Visas These visas allow to the foreign national temporary admission to invest, work, train or reside in the United States. Each visa has its own specific requirements, benefits, restrictions, and period of time. Some examples are listed below:
A-1Foreign government officials;
B-1/B-2Visitors for business/pleasure;
C-1Alien in transit;
D-1Crew-member departing on same vessel or arrival;
E-1/E-2/E-3 Treaty trader/investor/special category for Australians nationals;
F-1Student visa to study at a particular institution;
G-1 Representative of recognized foreign government (international organization);
H-1BVisa for professional skilled workers/fashion model/nurses/to attend a training program;
H-2A/H-2B Agricultural workers/unskilled workers for temporary or seasonal work;
IRepresentative of foreign information media/foreign professional journalist;
J-1 Exchange visitor visa;
K-1/K-3/K-4 Fiancé (e) of U.S. citizen/spouse of U.S. citizen under LIFE Act/children of K-3;
L-1A/L-1BIntra-company transferee visa for executives, managers/specialized knowledge personnel;
M Vocational student or non-academic student;
N-8/N-9 Parent of an alien classified SK-3 special immigrant/minor children;
NATO-1 Representative of member state to NATO;
O-1A Individuals with extraordinary ability in the arts, business, sciences, education or athletics;
O-1BIndividuals with extraordinary achievement in the motion picture or television industry;
P-1 Artists, athletes, and entertainment groups/support personnel;
QVisa for cultural exchange programs;
R-1Visa for Religious workers;
S-5/S-6Aliens supplying critical information relating to criminal organization/terrorism;
T-1Victim of severe form of human trafficking;
TNVisa for Canadians and Mexicans professionals under NAFTA;
UVictim of certain criminal activity who have suffered mental or physical abuse; and
VSpouse/child of an LPR and beneficiary of a family-based petition filed prior to December 21,2000.