Hello aspirant!

The JoSSA or Joint Seat Allocation Authority is the body that conducts counselling for admission into premier institutions like IIT, NIT, IIITs. JoSSA counselling is held before CSAB.

CSAB or Central Seat Allocation Board conducts CSAB counselling after JoSSA counselling is completed. This is to fill the vacant seats that remained unfilled in JoSSA counselling. Candidates who wish to try their luck again, can register themselves for CSAB counselling. Only those candidates who are not allocated any seat in JoSSA counselling, or who wants to upgrade their already alloted seat are eligible to apply. In both the counselling, the seats are filled on the basis of rank, reservation criteria, colleges preferred by the students.

For more information about CSAB counselling, go through the article below:

https://engineering.careers360.com/articles/csab

https://engineering.careers360.com/articles/csab-special-round-for-nits-iiits-and-gftis

The Joint Seat Allocation Authority (JoSAA) is the counselling procedure for candidates who have cleared both the levels of JEE (mains as well as advance). It is done in order to fill the seats in IITs, NITs, GFITs etc.

On the other hand, Central Seat Allocation Board (CSAB) is a special counselling which is conducted after JoSSA admission procedure is over. IT is done in order to fill the vacant seats, if any, in IIITs, NITs and GFTIs.