E-3 Classification - Available to foreign nationals who are nationals of the Commonwealth of Australia, and who are entering the U.S. to perform services in a "specialty occupation."
H-1B Classification - Used by foreign nationals who will be employed temporarily in a “specialty occupation” in architecture, engineering, mathematics, physical sciences, social sciences, medicine and health, education, business specialties, accounting, law, theology, and the arts.
A "specialty occupation" is defined as “one that requires theoretical and practical application of a body of highly specialized knowledge and attainment of a bachelor's or higher degree in the specific specialty (or its equivalent) as a minimum for entry into the occupation in the United States.”
J-1 Classification - The J-1 classification is available to individuals who intend to participate in an approved program for the purpose of teaching, lecturing, observing, and conducting research. The periods of authorized stays depends on the proposed activity and ranges from 6 months to 5 years.
O-1 Classification - available for temporary work and is available to foreign nationals who possess and who can document "extraordinary ability in the sciences, arts, education, business or athletics" demonstrated by sustained national or international acclaim."
TN NAFTA Classification - is for citizens of Canada or Mexico entering the U.S. to engage in the professional position. See NAFTA LIST