This means "Remote Location General Waitlist". Most likely, your journey on ticket starts from a station which is not the originating station for the train. Example, you have a train which starts from Bangalore and goes to Delhi. You book a ticket from a station like Guntakal. So, Guntakal will have a quota of X number of seats for this train. Once this gets filled up, you will be given a RLGN/RLWL kind of ticket. This will get confirmed, only if someone from That station cancels the ticket. Otherwise, you will have to wait for the chart to be prepared, which is about 4 hrs before departure from the station.
If ticket get fully confirm earlier before DOJ or at the time...
more... of chart preparation then it is RLGN if it is under RAC, WL then consider as RLWL