The B-1 visa is available to visitors for business and the B-2 visa is available to visitors for pleasure. The alien with a B visa is usually granted admission to the US for no more than six months. The alien can file in the US to extend this stay for an additional six months if they need more time to complete the purpose of the trip. Aliens coming to the US in B status cannot file to change their status to student unless they notify the border inspector upon entry into the US of his/her intention of applying to school in the US.
For nationals of certain countries an individual is permitted to come to the United States as a visitor for business or pleasure without obtaining a visa. The individual may enter on a visa waiver for up to 3 months. The individual is not permitted to extend his or her status or change to any immigrant or non-immigrant status.