A citizen of a foreign country who want to enter the United States generally must first obtain a U.S. visa, which is a travel document issued by the traveler’s country of citizenship. A US visa is a stamp that you get on your travel document, more specifically your passport, which means that you are eligible to enter the United States.
Citizens of some certain countries will not need a visa to traveling United States if they meet the requirements of visa-free entry.
How a US visa is used?
A US visa will allow its holder to travel to a port of entry, airport or land border crossing, and request permission of the Department of Homeland Security (DHS), Customs and Border Protection (CBP) inspector to enter the United States.
US visa application
The US visa application follows a similar and straightforward procedure for all types of visas. However, there are differences depending on the visa category and type you want to get. To apply for an American visa you must apply online to schedule an appointment with the US embassy or consulate in your home country.
US Visa Types
There are about 185 types of US visas, grouped into two main categories:
Nonimmigrant visas. Issued for temporary visits to the United States such as for tourism, business, employment, family visit, and studying.
Immigrant visas. Issued to people who will move permanently to the United States under immigrant investor schemes or family reunion.
Reading and Understanding a Visa