Deepak, OBC overall has 27% reservation. This 27% is spread across all sub divisions like BC-A/B/C/D/E. Now depending on the State you belongnto, the percentage of reservation changes. For example it is 4% in AP and 12% in Telangana. And this reservation is useful for securing seats in education field. For example, in Telangana out of every 100 MBBS seats, 12 seats are allotted to Muslims. This is 4 seats in AP. Now the merit list is prepared based on your marks and then the reservation is applied.