Before traveling to the United States, each citizen of a foreign country must generally obtain a “nonimmigrant visa” for temporary stay or an “immigrant visa” for permanent residence. The type of visa you will need is based on the purpose of your travel.
All foreign nationals or aliens entering the United States are generally required to present a passport and valid visa issued by a U.S. Consular Official, unless they are a citizen of a country eligible for the Visa Waiver Program (VWP), or are a lawful permanent resident of the U.S., or a citizen of Canada.
The Visa Waiver Program allows foreign nationals from designated countries to be admitted to the U.S. under limited conditions and for a limited time without obtaining a visa. Learn more about the VWP here: https://travel.state.gov/content/travel/en/us-visas/tourism-visit/visa-waiver-program.html
Nationals of VWP Designated Countries may be able to submit an online request at www.VisaCentral.com for travel authorization via the Electronic System for Travel Authorization (ESTA). This allows visitors from participating countries to get speedy approval for travel to the United States for business or pleasure for 90 days or less.
For more information, visit: https://travel.state.gov/content/travel/en/us-visas.html