Hi Harikrishnan.

PWBD refers to Persons With Benchmark Disability as per the rights of persons with disability act, 2016. Candidates who have any disability will have to fill 'Yes' in this field.

Check the specified Disability Clause using the link below-

www.aiimsexams.org/pdf/PWBD%20clause.pdf

OBC (NCL)- refers to Other Backward Caste and belonging to Non creamy Layer on the basis of the income of your family, hope this helps, good luck