About ESTA:
http://www.esta.us/
What is ESTA?
ESTA stands for Electronic System for Travel Authorization. ESTA is an online application system developed by the United States government to pre-screen travelers before they are allow to board an airplane or ship bound for the United States. Starting on January 12, 2009, any person entering the United States under the visa waiver program is required to hold an approved ESTA Travel Authorization.
Who Needs to Apply for ESTA?
All travelers entering the United States (by air or sea) under the visa waiver program are required to hold a valid ESTA travel authorization. The purpose of ESTAis to allow DHS to pre-screen all Visa Waiver Travelers before they leave their respective countries. U.S.-bound travelers are recommended to apply for a Travel Authorization at least 72 hours prior to departure.
What is the Visa Waiver Program?
The visa waiver program is a U.S. government program that enables citizens and nationals from the Visa Waiver Countries to enter the United States for tourism or business purposes for up to 90 days without obtaining a visa. The advantage of entering the United States under the visa waiver program is that you can travel to the United States on short notice without obtaining a visa.
Apply for ESTA here:
https://esta.cbp.dhs.gov/esta/application.html?execution=e1s1