A waitlisted ticket has no berth and no guarantee of one. The number after WL is how many people are ahead of you in that quota’s queue; it falls as passengers ahead cancel or are confirmed from other quotas. A PNR shows two waitlist numbers: the one at booking and the current one, and only the current one matters.
The letters before the number are what decide your odds. GNWL clears from the largest pool; RLWL, PQWL and RSWL from small ones; TQWL barely moves. A fully waitlisted e-ticket is cancelled automatically at charting and refunded minus clerkage, and it is not valid for travel.
Also written or searched as: waiting list · waitlist · WL ticket · waiting ticket · WL meaning