Employers who wish to hire foreign workers for temporary period for services or to receive training may file an I-129 petition. In most cases, workers who enter the United States under this petition must depart the U.S. when their maximum period of stay has been reached. Form I-129 may also be used to petition for an extension of stay or change of status for certain non-immigrants.
There are many categories of workers who are temporary visitors symbolized by letters which generally correspond to the visas issued by the State Department.
H-1B: Specialty Occupation
H-2B: Temporary Non-agricultural Workers
L-1: Intracompany Transferee
O-1: Extraordinary Ability