The J Visa is meant for exchange visitors, and there are many categories of applicant types within the J Visa, each with their own set of requirements.
Within the Private Sector Programs are the following categories:
Au Pair
Camp Counselor
Foreign Physician
Summer work/travel
Trainee
Within the Government Programs are the following categories:
Government Visitor
International Visitor (reserved for U.S. Department of State use)
Student, secondary
Student, college/university
Professor
Research Scholar
Short-term Scholar
Specialist
Teacher
Applicants must demonstrate that they properly meet the requirements to be issued an exchange visitor visa, including the following:
That they plan to remain in the U.S. for a temporary, specific, limited period.
Evidence of funds to cover expenses in the United States.
Evidence of compelling social and economic ties abroad; and other binding ties which will insure their return abroad at the end of the visit.
In addition to these requirements you will need to make sure you meet the requirements for your particular category as well.
For more information, or for help determining and obtaining the right VISA for you, please consider a legal consultation.