What exactly is a visa?

Question

not the credit card company but the one for moving to countries.

Answer 1

It is the formal approval (in the form of a stamp, or an insert page in your passport) given to you by the government of a country, allowing you to visit that country for a stipulated length of time and often for a specific purpose (educational course, vacation, business, etc..).

Answer 2

IN the US, this is how a visa is defined.

A visa doesn’t permit entry to the U.S., however. A visa simply indicates that your application has been reviewed by a U.S. consular officer at an American embassy or consulate, and that the officer has determined you’re eligible to enter the country for a specific purpose.

A visa allows you to travel to the United States as far as the port of entry (airport or land border crossing) and ask the immigration officer to allow you to enter the country. Only the immigration officer has the authority to permit you to enter the United States. He or she decides how long you can stay for any particular visit. Immigration matters are the responsibility of the U.S. Department of Homeland Security.

There are two categories of U.S. visas: immigrant and nonimmigrant.

Immigrant visas are for people who intend to live permanently in the U.S. Nonimmigrant visas are for people with permanent residence outside the U.S. but who wish to be in the U.S. on a temporary basis – for tourism, medical treatment, business, temporary work or study. **