WL = Waiting List.
When the train is full, IRCTC starts a waiting list. The number shows your queue position:
WL 5— 5th in lineWL 1— Next to be confirmed if any cancellation happens
Online (e-tickets): If WL does not clear by chart preparation (~4 hours before departure), your ticket is automatically cancelled and refunded to your IRCTC account.
Counter tickets: WL counter tickets are valid even if not cleared — you can board, but the TTE will allot any vacant seat or you may travel as standee/general.
Waiting list types: GNWL (General), PQWL (Pooled Quota), TQWL (Tatkal), RLWL (Remote Location), CKWL (Tatkal), RSWL (Roadside).