Passport and entry permit
Most EU nationals are allowed to travel to the US on vacation and stay for up to 90 days without a visa. To be able to do this, you must apply for the entry permit ESTA. An application should preferably be made no later than 3 days before departure. An approved ESTA application is valid for 2 years, or for as long as the passport is valid.
Most EU nationals do not need a visa for entry into the US, but an entry permit (ESTA) and a machine-readable e-passport are needed. You must apply for your entry permit at least 72 hours before departure in order to obtain a permit for boarding. It is important that the information in your registration matches the information in your passport. You have to apply and pay for your own entry permit, which is valid for two years following approval. An application costs $ 14. Application for the entry permit ESTA must be done at their official site. You must present your application number at the check-in at the airport.
Make sure to investigate which rues apply for your specific country prior to booking your trip.
E-passport / Biometric passport
From April 1, 2016, in addition to an approved ESTA application, you must have an electronic passport that is valid throughout your stay in the United States. The e-passport is marked with a special symbol on the front and has an embedded electronic chip.
An E-passport is the same as a biometric passport.