There are several types of visa:
The Waiver Pilot Program Visa
The program allows citizens of certain selected countries, traveling temporarily to the United States under the nonimmigrant admission classes as visitors for pleasure and visitors for business, to enter the United States without obtaining nonimmigrant visas. Admission is for no more than 90 days. The program was instituted by the Immigration Reform and Control Act of 1986 (entries began 7/1/88). Under the Guam Visa Waiver Program, certain visitors from designated countries may visit Guam for only up to 15 days without first having to obtain nonimmigrant visitor visas. The Visa Waiver Program was made permanent in 2000.
Tourist and business visas
Business travelers may enter the United States using a B1, or 'Visitor for Business' Visa. In practice these visas are invariably issued jointly with B2, or 'Visitor for Pleasure' (i.e. Tourist) visa. This practice means that, if a candidate has an old tourist visa, it may be valid for a planned business trip.
Visa E1 or E2: investor visa:
E1: Nationals of qualifying Treaty countries who undertake a significant amount of international trade with the United States may qualify for this type of visa. The volume of such trade must be sufficient to justify the trader or his/her employee(s) being in the United States to manage the trade, and must constitute the majority of the trader's international trade (i.e. at least 50% of the Trader's exports/imports must be to/from the USA). There is no set minimum level of trade which is considered sufficient, but obviously the lower the volume of trade the less likely one is to qualify as a Treaty Trader.
E2: Nationals of qualifying Treaty countries who have made a significant investment in the United States may qualify for E2 Treaty Investor status. Like the E1 visa, there is no set minimum level of investment which may qualify for E2 status, but the lower the investment the less likely one is to qualify. Again, the level of investment must be sufficient to justify the treaty national (or his/her employees) presence in the United States. The investment must be in an operating business – i.e. simply buying property or stocks and bonds does not qualify. Also, a substantial part of the investment must have been made before applying for E2 status.
F1: The "F1" visa is for academic studies. An F1 visa is issued to students who are attending an academic program or English Language Program. F1 visas are by far the most common form of international student visa in the U.S. F1 students must maintain the minimum course load for full-time student status. F-1 status allows for part-time, on-campus employment (fewer than 20 hours per week). Additionally, students can work on optional practical training (OPT) for up to one year after completion of their academic program. Students are expected to complete their studies by the expiration date on the I-20 form (Certificate of Eligibility for Nonimmigrant Student Status).
J1: A J1 visa is issued to students who need to obtain practical training that is not available in their home country to complete their academic program. J-1 student status allows for similar employment as the F-1 visa, with similar restrictions, as long as permission is given by the exchange visitor program sponsor.
M1: An M1 visa is issued to a student who is going to attend a non-academic or vocational school. M-1 visa holders for technical and vocational programs are not permitted to work during the course of their studies. The M-1 student visa applicants must have evidence that sufficient funds are immediately available to pay all tuition and living costs for the entire period of intended stay.
H1B: The US H1B visa is a non-immigrant visa that allows US companies to employ foreign workers in specialty occupations that require theoretical or technical expertise in specialized fields such as in architecture, engineering, mathematics, science, and medicine. Under the visa a US company can employ a foreign worker for up to six years.
H2B: The H2B visa is available to employers of foreign workers not working in the agricultural field. This visa is only available for work that is temporary in nature.
L1A and L1B: For executives or managers who have worked for at least one of the past three years for a foreign parent, subsidiary, affiliate, or branch office of the US company that will employ them. For specialized knowledge employees who have worked for at least one of the past three years for a foreign parent, subsidiary, affiliate, or branch office of the proposed US employer
J1: The Exchange Visitor (J) non-immigrant visa category is for individuals approved to participate in work-and study-based exchange visitor programs. Participants are integral to the success of the program. Here you can learn more about obtaining the J-1 Visa and other relevant visas.
J2: The J-2 Visa is a non-immigrant visa issued by a consular official at a U.S. embassy or consulate for spouses and dependents (unmarried children under the age of 21) of J-1 exchange visitors who accompany or later join the J-1 holder in the United State