Unreserved and Reserved train means they have tickets. But in Reserved train the berth of the train are specified, that you see in your ticket like S6, 8 UB. Reserved Trains to have Unreserved coaches which means you have to purchase ticket but like reservation they too have ticket but the seats and berth are not specified.
So in DEMU they too have tickets but seats and berth are not specified. So they don't appear in the IRCTC website.