B-1 Visa: The B-1 visa is a temporary visa category reserved for business activities. While the scope of the visa is broad and covers a variety of business activities, including consulting with business associates or a U.S. client, travel to conventions in the United States, contract negotiations, and estate settlement, B-1 visitors cannot be paid or compensated in the United States. The limits on the scope of business activity under a B-1 visa make it especially important that you consult with a legal professional to confirm that your intended activities are lawful under the terms of your immigration status.
B-2 Visa: The B-2 visa is also a temporary visa category reserved for short-term trips to the United States of a nature involving tourism, a family visit, or medical treatment.
(Source: www.uscis.gov, visit “Visitors to the United States”; http://travel.state.gov/visa/temp/types/types_1262.html)