Hii!
Frankly speaking, there are no types of private candidate for Board exams, however, candidates must be appearing for the exam due to different reasons. May be private candidates because they are taking any professional coaching for competitive exams such as jee and neet. Some may be there as they are giving improvement exam or re- exam as they failed in certain subjects etc., So there can be other reasons too.
Hope this helps.
Good luck!
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