Seats are reserved for Home state students in NITs. It is given to the students who belong from that state.

 Home State (HS) Quota: In NITs, 50% of the seats are reserved for this quota.

Other State (OS) Quota: Under this quota, there is nearly 50% reservation of seats for candidates belonging to all other states and Union Territories excluding the Home state.

To know in detail you can also refer below article

http://www.engineering.careers360.com/articles/jee-main-know-about-reservations-quotas-and-categories-in-detail

Good Luck!!