Visa Waiver Program
A program that allows nationals from certain countries to come to the United States without a visa, so long as they're planning on being tourists, and to leave within 90 days. Persons coming to the United States under this program receive green-colored I-94 cards. They are not (except in rare cases) permitted to extend their stay or change their statuses. For example, someone who enters on the visa waiver program cannot then ask to stay on as a student, but would have to leave the U.S. and apply for a student visa.