Those from a foreign country who want to come into the United States usually need a visa to do so. There are two main types of visas: non-immigrant and immigrant. People who plan on a temporary stay need non-immigrant visas. Immigrant visas are for those who wish to live permanently in the U.S. The type of visa necessary is determined by immigration law and directly relates to the purpose of your travel.
Business visitor visas
The B-1 visa allows non-immigrants to temporarily enter the United States for business. International travelers with business visitor visas make up a large part of temporary visitor travel to the U.S. each year.
Pleasure, tourism, medical treatment
The B-2 visa is for visitors who come to the U.S. for recreational purposes -- tourism, amusements, visiting family, etc. Visitors on this visa are prohibited from legal employment in the US during their stay.
H-1B visas allows people with highly specialized knowledge to temporarily come into the country. This is a wide-ranging visa. It covers the aforementioned specialized instances, but also those involved in government-to-government research and development. The L visa is another type of temporary work visa. It's for intracompany transferees who, within the last three years, have been employed abroad continuously for one year and will be employed by a branch of the same company in the U.S. The worker needs to hold a managerial, executive or specialized position within the company to qualify for an L visa.
Student visas have a long list of requirements to be met for non-immigrant students to be accepted for enrollment at an established school that has the requisite certification. In general, academic students, including those in language training, need an F visa. Non-academic vocational students need an M visa.
If you plan on being an exchange visitor, you need to be accepted in an exchange program to qualify for a J visa. When the program is over, you're expected to head back home in order to use what you've learned. There are designated sponsoring organizations which facilitate these types of visits.
Diplomats and foreign government officials
Diplomats and foreign government officials need to qualify for an A-1 or A-2 visa to travel to the U.S. on behalf of their national government to engage in official activities. The U.S. State Department will determine if your duties are governmental and subsequently if you qualify for an A visa. Government officials in the country for commercial work or as tourists do not qualify for A visas. Government officials can't travel on tourists visas or visa free under the visa waiver program. They need to obtain an A visa prior to coming into the United States.
Foreign media, press and radio
I visas are for foreign media in the U.S. This visa works under the rules of reciprocity. If other governments require U.S. press members to adhere to certain procedures and fees, the U.S. takes that into consideration when considering an applicant for a media visa.
Extraordinary ability in sciences, arts, education, business or athletics
Type O-1 visas are applicable to "individuals with extraordinary ability or achievement" in the sciences, arts, education, business, athletics or the motion picture / television field. Visa type O-2 is basically a complimentary one for people accompanying an O-1holder to assist in an artistic or athletic performance for a specific event or performance can receive an O-2 visa. Both are non-immigrant visas for people who wish to work temporarily in the United States.
The R type visa applies to people who want to come into the country to work temporarily in a religious capacity. An applicant must belong to a recognized religious denomination that has non-profit organizations in the U.S. for at least two years before applying for this visa.
Treaty traders and treaty investors
The E-1 visa is for a Treaty Trader and the E-2 version is for a Treaty Investor. These are for visitors from a country with which the U.S. maintains a treaty of commerce who are in the States to conduct a high level of trade or to develop the enterprise between the two countries.