A Waiting List Ticket (WL) is issued when there are no more reserved seats available to be booked. Indian Railways follows different quotas for each running train, with each quota in a train having a fixed number of reserved seats in different classes.
1) GNWL - General Waiting List : A Ticket with a GNWL is issued when the Source station of the passenger is the Source station of the train or one of the stations near to it.
--This quota has the highest number of seats in any given train and has the highest probablity of getting confirmed at the time of final charting.
2) PQWL - Pooled Quota Waiting List - Most trains has a defined pooled quota which is used if you start from the Source station of the train but terminate at some station before the Destination of the train.
--This has fewer seats as compared to GNWL, thus a lesser probability for cofirmation.
3) RLWL - Remote Location Waiting List : Most trains have important stations marked as Remote Locations in the route, which mark the beginning of the RLWL quotas in the train.
-- Even this quota has a fewer number of seats as compared to GNWL.