The H-3 Visa is specifically designed to enable you to train in the US in almost any discipline. USCIS loosely calls this classification one for ‘any field of endeavor’. This includes agriculture, technology, communications and governmental leadership. However it does not include people seeking graduate medical training. Your spouse and unmarried children under the age of 21 are allowed to join you in the US under the H-4 status. Family members are not permitted to work while in the US.
The H-3 Visa is not self-petitioned. An employer must petition on behalf of the trainee. The employer must provide certain evidence about the training, including a description of the training program, your compensation (if any) and reasons why you need the training. The employer must then submit a petition on Form I-129 with the regional USCIS center that has jurisdiction over the place where the training will be offered.