Key aspects of the Visa Waiver Program include:

Eligible countries: The VWP currently includes 39 countries whose citizens are eligible to participate in the program. These countries are typically considered to be low-risk in terms of security and immigration violations, and they have reciprocal agreements with the United States regarding visa-free travel for short stays.
Travel purposes: The VWP allows eligible travelers to visit the United States for tourism, business meetings, conferences, or other short-term purposes, provided they adhere to the program’s conditions and restrictions. However, VWP travelers are not permitted to engage in paid employment, study for credit, or stay for longer periods than authorized under the program.
ESTA application: Before traveling to the United States under the VWP, eligible travelers must apply for authorization through the ESTA system. The ESTA application collects biographical information, passport details, travel itinerary, and eligibility questions related to health, criminal history, and immigration violations. Approval or denial of an ESTA application is usually provided almost immediately, although travelers are advised to apply at least 72 hours before their intended departure.
Authorization period: Once approved, ESTA authorization is valid for two years or until the traveler’s passport expires, whichever comes first. During this period, travelers can make multiple trips to the United States for stays of up to 90 days each time, provided they comply with the terms and conditions of the VWP and ESTA program.
Entry requirements: While VWP travelers do not require a visa for entry into the United States, they must meet certain entry requirements upon arrival, including possession of a valid passport from a VWP country, a return or onward ticket, and compliance with U.S. immigration laws and regulations. Additionally, travelers may be subject to inspection by U.S. Customs and Border Protection (CBP) officers upon arrival at a U.S. port of entry.