The ESTA form must be completed by all visitors from countries that are part of the Visa Waiver Program (VWP). In fact, if you do not complete the online form and you do not receive travel authorization, you will not be allowed to travel to the United States unless you already have a visa.
For this reason the ESTA form must be obtained individually, be it a friend or family members who wants to enter the United States, every traveler must have his or her own ESTA, even children and newborns. ESTA can be issued for tourism, for business trips, for short medical treatment and short study periods (less than 18 hours per week).
It is also permitted to apply for ESTA on behalf of a third party.
Example 1: Alexandre
Alexandre has French nationality, enabling him to be admitted to the Visa Waiver Program. Next week, he will go find his longtime friend, Francis, living in Miami for several years. Before Alexis bought his plane ticket, Francis had already obtained an ESTA travel permit for him. This was necessary so Alexander could fly by which he would join his friend for several weeks.
Example 2: Sabrina
Sabrina lives with her family in Berlin. For Christmas, they chose to go on vacation in Acapulco, Mexico. Their flight will stop in New York. Sabrina and her family will have to obtain an ESTA for each member of the family before they can embark for their final destination. In fact, even though they will only be in transit, Sabrina and her family being German and Germany being a country included in the VWP, each member of the family must have a valid ESTA to enter the United States.