The Visa Waiver Program (VWP) enables nationals of certain countries to travel to the United States for tourism or business stays of up to 90 days without first obtaining a visa. Business visitors under this program are granted WB status (WB stands for Waiver-Business).
People who are not from one of the countries on the VWP list must, in most cases, apply to a U.S. embassy or consulate for a tourist or business visa before traveling. Although VWP travelers need not do this, they will have to get advance confirmation of their eligibility to travel to the U.S. under the VWP through a program known as ESTA (Electronic System for Travel Authorization.)
There is no cap on the number of people allowed to enter the United States under the WB category each year nor on the number of nationals of a country admitted to the United States using this category.
WB eligibility requirements are very specific.
Nationality: You must be a national of a country under the Visa Waiver Program. See the list on the "Visa Waiver Program" page of the State Department's website. Countries are chosen for this list based on their having met various security standards and other requirements, such as sharing security data with the United States and providing timely reports of both blank and lost and stolen passports.
Business Purpose: - You must be traveling to the United States for business. The definition of business is the same as if you were applying for a B-1 visa. As possible examples of business purposes, the State Department gives consulting with business associates, traveling to a scientific, educational, professional, or business convention, attending a conference, settling an estate, or negotiating a contract. However, coming to the U.S. to work for pay is not among the allowed purposes.
Period: – Your intended stay in the U.S. must not exceed 90 days.
It's important to realize that the VWP is not a free entry pass. If, upon coming to the U.S., the border officials determine that your true intent is some activity other than business, you may be told you should have applied for the appropriate visa and sent home.
There is small fee ($4 in mid-2011) for the ESTA authorization. If you will be entering through a land port, you must also pay a small land border fee.
You'll need to come to a U.S. port of entry with the following:
Although you can engage in a business activity, you cannot take up employment in the United States. If you remain in the United States after the maximum 90 days without any change in your status, you will be considered out of status. With only a few exceptions (such as if you have become the immediate relative of a U.S. citizen), you cannot change your status without leaving the United States.
The 90-day period of stay cannot be extended under any circumstances.
You cannot, with few exceptions, apply for adjustment of status and lawfully seek to become a legal permanent resident while on WB status. Talk to a lawyer if you believe you may separately qualify for U.S. permanent residence (a green card). Your best bet may be to first leave the U.S. and then apply to enter on your new status.