Visitors arriving in United States for business purposes require a valid business visitor visa namely BI visa or an ESTA (Electronic System for Travel Authorization).
A Bi visa is a non-immigrant visa that allows visitors to visit the United States temporarily for business purposes only. They may get involved in business activities like consultation with business associates, conferring contracts and attending seminars or conferences in the US.
Visitors travelling for business purposes from participating VWP (Visa Waiver Program) nations may be required to procure an ESTA before leaving for their trip.