B-1/B-2 Visa
A B-1 visa is issued to a foreign citizen seeking to enter the United States of America for business purposes, while a B-2 visa is granted to a foreigner seeking to enter for tourism purposes. In practice, the two visa categories are usually combined together and issued as a "B1/B2" visa valid for a temporary visitor for either business or pleasure or a combination of the two.

E-1 Visa
The E-1 Treaty Trader Visa allows foreign nationals of eligible countries to enter the United States in order to engage in trade of a substantial nature between the United States and the applicant's country of nationality. The trade involved must be an international exchange of items between the United States and a treaty country.

F-1 Visa
F-1 visa is reserved for non-immigrants wishing to pursue academic studies and/or language training programs. F-1 visas are given only through academic institutions. Vocational education is not included in F-1 visa; for vocational education, an M visa should be obtained.

G-4 Visa
G-4 visas are issued to individuals who are proceeding to the United States to take up an appointment at a designated international organization, including the United Nations.

H-1B Visa
The H-1B is a non-immigrant visa in the United States . It allows U.S. employers to temporarily employ foreign workers in specialty occupations. If a foreign worker in H-1B status quits or is dismissed from the sponsoring employer, the worker can find another employer, apply for a change of status to another non-immigrant status, or must leave the US.

I-1 Visa
I-1 visa is suitable for Foreign professionals in print and film media such as reporters, film crews, video tape editors, or employees of independent production companies; freelance journalists working under contract, and persons in similar occupations.

J-1 Visa

A J-1 visa is a non-immigrant visa issued by the United States to exchange visitors participating in programs that promote cultural exchange. Applicants must meet eligibility criteria and be sponsored either by a private sector or government program.

J-1 visa holders are expected to leave the United States for their home country upon the completion of their J-1 program. For the purpose of travelling exchange visitors are granted a 30-day grace period in addition to the time determined by their program. All holders of J-1 visas are required to be entered into the SEVIS tracking system.

K-1 Visa
A K-1 visa is a nonimmigrant visa issued to the fiancé(e) of a United States citizen to enter the United States. A K1 visa requires a foreigner marry his or her US citizen petitioner within 90 days of entry, or leave the US. Once the couple marries, the foreign citizen can adjust status to become a lawful permanent resident of the United States. Although a K-1 visa is legally classified as a non-immigrant visa, it usually leads to important immigration benefits and is therefore often processed by the Immigrant Visa section of United States Embassies and Consulates worldwide.

L-1 Visa
An L-1 visa is a visa document used to enter the United States for the purpose of work in L-1 status. It is a non immigrant visa, and is valid for a relatively short amount of time - generally three years. L-1 visas are available to employees of an international company with offices in both a home country and the United States, or which intend to open a new office in the United States while maintaining their home country interests. The visa allows such foreign workers to relocate to the corporation's US office after having worked abroad for the company for at least one year prior to being granted L-1 status. The US office must be a parent company, child company, or sister company to the foreign company.
Spouses of L-1 visa holders are allowed to work, without restriction, in the US, and the L-1 visa may legally be used as a steppingstone to the Green Card under the doctrine of dual intent.

M-1 Visa
The M-1 visa is a type of student visa reserved for vocational and technical schools. To obtain an M-1 visa for traveling to the United States, a student must present a signed Form I-20 at a United States embassy or consulate in his home country. The I-20 is issued by a designated school official, typically the international student adviser, after the student has fulfilled a school's admissions requirements and presented proof of financial resources.
M-1 students are admitted into the United States for a fixed time period. When they cross the border, their I-94 departure cards are stamped with a date, unlike students with an F-1 visa. They may stay for the length of their training program plus any Optional Practical Training, plus a thirty-day grace period at the end of their training. Their stay may not exceed one year unless they are granted an extension for medical reasons. If a student violates his status by, for example, not maintaining a full course of study, he is not eligible for the grace period.
Students in M-1 status may not work on or off campus while studying, and they may not change their status to F-1.

N Visa
The N visa category is reserved for a "child" (who is unmarried and under the age of 21) of an officer or employee, or of a former officer or employee, of a foreign government which is also a member of an international organization (NATO included. In general, N nonimmigrant classification may be granted for up to 3 years with possible 3 years extension (in increments) as long as the petitioner remains a "child." While holding N visa status, the person is permitted to be employed by obtaining an Employment Authorization Document. 

O-1 Visa
The O-1 classification is a type of employment visa under United States immigration law that applies to aliens who have extraordinary ability in the sciences, arts, education, business, or athletics which has been demonstrated by sustained national or international acclaim and who are coming temporarily to the U.S. to continue work in the area of extraordinary ability.

P Visa
The P classification is a type of temporary employment visa, under United States immigration law, which applies to foreign-based athletes and entertainment groups.

Q-1 Visa
The "Q-1" visa is for certain international cultural exchange programs designed to provide practical training and employment, and sharing of the history, culture, and traditions of participants home country in the United States.

R Visa
Immigration and Nationality Act provides a nonimmigrant visa category "R" for individuals seeking to enter the United States to work in a religious capacity on a temporary basis. Religious workers include individuals authorized by a recognized employing entity to conduct religious worship and to perform other duties usually performed by authorized members of the clergy of that religion, and workers engaging in a religious vocation or occupation.

TN Visa
TN (Trade NAFTA) status is a special non-immigration status unique to citizens of the United States, Canada and Mexico. It allows American, Canadian and Mexican citizens the opportunity to work in each other's countries in certain professional occupations. Within the TN set of occupations, an American, Canadian or Mexican can work for up to three years (until October 16, 2008, one year) at a time. However, the TN status may be renewed indefinitely in three-year increments.

EB-5 Visa
This visa provides a method of obtaining a green card for foreign nationals who invest money in the United States. To obtain the visa, individuals must invest at least $1,000,000 USD, creating at least 10 jobs. By investing in certain regional centers with high unemployment rates, the required investment amount is $500,000. The investment could only be received by an economic unit defined as a Regional Center.