Citizens of certain countries need neither a B-1 or B-2 visa to come into the United States for business or pleasure. These countries include most European countries, Canada, and Australia. Visitors under the Visa Waiver Program can stay in the United States for up to 90 days, and cannot change your immigrant status while you are visiting.
The complete list of countries is: Andorra, Australia, Austria, Belgium, Brunei, Denmark, Finland, France, Germany Iceland, Ireland, Italy, Japan, Liechtenstein, Luxembourg, Monaco, the Netherlands, New Zealand, Norway, Portugal, San Marino, Singapore, Slovenia, Spain, Sweden, Switzerland, and the United Kingdom. However, these people must have a return ticket and cannot change their visa status once they enter the country.