CSAB (Central Seat Allocation Board) and JoSAA (Joint Seat Allocation Authority) are both involved in the seat allocation process for engineering admissions in India, but there are some differences between the two. The basic difference is that first, JoSAA completes its JEE Main Counselling process for admissions across IITs, NITs, and other participating colleges. Then, CSAB conducts two rounds to fill up the vacant seats (if any) of NITs, IIITs, and other colleges (this does not include IITs).