Some constituencies are reserved for people who belong to the backward classes like the Scheduled Castes [SC] and Scheduled Tribes [ST]. In a SC reserved constituency only someone who belongsto the Scheduled Castes can stand for election.
Similarly only those belonging to the Scheduled Tribes can contest an election from a constituencyreserved for ST. Currently, in the Lok Sabha, 84 seats are reserved for the Scheduled Castes and 47for the Scheduled Tribes.
It is a measure to include representation for all classes in the legislature.