According to regulations,  the following applicants can obtain J-1 visa:

(a) A student, for the purpose of pursuing formal courses, or any combination of courses, research, or teaching, leading to a recognized degree or certificate, in an established school or institution of learning. Upon receipt of a degree or certificate, a student may be granted up to a maximum of 18 months of practical training provided:
(1) The training is needed to round off the academic studies,
(2) The training is not available in the student's home country,
(3) The training is directly related to the academic program, and
(4) The training is authorized in writing by the Responsible Officer of the exchange visitor program involved;
(b) A trainee, for the purpose of obtaining on-the-job training with firms, institutions and/or agencies in a specialized field of knowledge or skill for periods not to exceed 18 months;
(c) A teacher, for the purpose of teaching in established primary or secondary schools, or established schools offering specialized instruction;
(d) A professor, for the purpose of teaching or conducting advanced research, or both, in an established institution of higher learning;
(e) A research scholar or specialist, for the purpose of undertaking or participating in research or in demonstrating specialized knowledge or skills;
(f) An international visitor, for the purpose of travel, observation, consultation, research, training, sharing, or demonstrating specialized knowledge or skills, or participating in organized people-to-people programs; or
(g) A professional trainee, for the purpose of pursuing clinical training in the medical and allied fields.

Above categories are not inclusive.  Other worker such as Au Paire can also get J-1 visa.