ESTA is an electronic system for travel authorization that is automated to give visitors a right to travel to the United States after you have registered for their visa waiver program. USA ESTA is only available to citizens of certain countries.
It is a system that collects web-based data that determines the eligibility of visitors to the USA to travel to that country for business or other legitimate reasons. ESTA only applies to foreign nationals who are not US citizens. The visa waiver program has certain conditions and once you have this waiver, applying for ESTA allows you, a foreign national to the USA, to travel in that country without the need for a visa or green card. If a person already has a visa granted by US embassies all over the world, that person does not need to go through the ESTA process.
USA ESTA is a specialist visa waiver application, and once you have this authorization, you need not have a USA visa if you plan to go to that country. This authorization must be applied for at least three days before you plan to travel, and all applications have to be made electronically over the net. These visas are only valid for ninety days, so in case you do intend to stay longer, you must apply for a regular visa. It is important that you check whether you have a passport that can be read by a machine. This passport will have chevrons at the end of the personal information page. Your passport must also have an electronic chip or a digital ID photograph. Your application for authorization for ESTA must give all your flight details including the airport from which you are flying to the United States. You are then allotted an application number which you need to have with you at all times during your travel.