The Electronic System for Travel Authorization or US ESTA Visa is an application process available to those traveling to the United States without a visa from a Visa Waiver Country only. Once you obtain an approved ESTA APPLICATION, it is viable for a period of two years with the exception of passports that run out before this period is over. For each time you visit the USA whether for business, leisure or medical purposes, your approved travel authorization or ESTA gives you a maximum amount of 90 days per stay.
Your ESTA Visa is valid for two years from receipt unless your passport expires within this time frame. If you are only residing in the United States for a short period less than 90 days, you can easily apply for ESTA and avoid the long-winded Visa application process. ESTA is not just for British Nationals who are visiting the United States. It also applies to all foreign nationals of the countries within the Visa Waiver Program (VWP) who are using Great Britain as a stop-over on route to the United States. ESTA Visa is also needed if you are a citizen or national from one of the countries within the VWP flying to Great Britain from the USA. However, if you are residing in the USA for a greater amount of time than the 90 days specified or if you are ineligible to enter under the VWP, then you will not be authorized to visit. It is worth bearing in mind that obtaining an ESTA only allows you to travel to the United States without a Visa for America. It does not automatically give you permission to enter this will be granted by the immigration officer at your destination of arrival in the United States.
The Visa application or typical American Visa process is much more complex and lengthy (e.g. visiting the American Embassy). Whereas the requirements you need to obtain ESTA USA Visa are less time-consuming and not as complicated. You will need to complete the online application form and in order to process it, you should also have your machine-readable passport and your credit card ready to pay and complete the process. Do not worry about having your flight details or even your place of stay while in the USA (e.g., hotel reservation). All of this information can be provided where necessary once you have obtained ESTA Visa for USA or prior to travel via the ESTA form.
The ESTA US Visa application system is only available online which means there are no forms that need printing, and you have no need to visit the American Consulate or Embassy. Do remember that if you are NOT a citizen of one of the countries belonging to the US Visa Waiver Program, then you are unable to apply. However, if you are, then you are at liberty to submit an application, so you need to be sure before beginning your online form. Do find out whether you are suitable for taking the ESTA eligibility test.