See PwD means Person with Disability. Now as you know there are PwD candidates and they also belong to different reservation category as well. So Open PwD means that a candidate who is a PwD and belong to the unreserved category. similarly there are SC-PwD, ST-PwD etc.

To know more about JOSAA counselling visit the link below:

https://engineering.careers360.com/articles/josaa-counselling

I hope this answer helps. All the very best for your future endeavors!