ESTA stands for Electronic System for Travel Authorization. It's an automated system that determines the eligibility of visitors to travel to the United States under the Visa Waiver Program (VWP). Travelers from VWP countries need to obtain an approved ESTA before boarding a carrier to travel by air or sea to the United States.

No, if you already have a valid U.S. visa, you do not need to apply for ESTA. ESTA is specifically for travelers who are eligible to enter the U.S. under the Visa Waiver Program.

It's recommended to apply for ESTA at least 72 hours before your travel. However, you can apply at any time before boarding. It's advisable not to wait until the last minute to avoid any potential issues or delays.

An approved ESTA is valid for two years from the date of authorization or until the expiration of your passport, whichever comes first. During this period, you can make multiple trips to the United States for up to 90 days each visit.

Once you've submitted your ESTA application, you cannot update the information provided. However, you can reapply for a new ESTA if there are any changes to your circumstances or if you need to update your travel information.

The ESTA application requires basic personal information such as your full name, date of birth, passport details, contact information, employment details (if applicable), and information about your travel plans, including the address of your accommodation in the U.S.

Once your ESTA application is approved, you will receive your authorization via email. It's essential to provide a valid email address during the application process and to check your spam or junk folder if you do not see the email in your inbox.

No, ESTA is only valid for entry into the United States by air or sea. Travelers entering the U.S. by land from Canada or Mexico or by ferry from Canada must present a valid passport but do not need an approved ESTA.