US government started online application program that names is (VWP) Visa Waiver Program are provides to make traveling to US without any problem but only for short visits and you have to come back within 90 days.It included some countries in the program and the selection of countries was made according to US security guidelines. Today travelers from VWP participating countries enjoy traveling to US with ESTA Visa US.
Visa is the general word and the permission is also like a visa. When you get permission to visit the country US and you can enjoy but electronic authorization is different from the regular visa in technical terms. A regular visa could be for a long time like one year but the ESTA Authorization is valid only for 90 days.
ESTA USA Visa Application Online Form can be rejected if any information provided is found to be wrong or ambiguous and permission is valid for two years but stands cancel in case the traveler gets a new passport or changes his name or the government change eligibility for electronic application.