@guest: Re# 91771-0
RAC means Reservation Against Cancellation!
An RAC ticket gets you on the train (A WL ticket doesn’t) and in your chosen class, but there’s a chance you could end up with just a seat.
A berth is split into 2 seats for 2 RAC ticket holders, if there’s any last minute cancellations, or if any quota allocations remain unsold, or if...
more... any confirmed ticket holders are given a free upgrade (more later), an RAC ticket holder is given the empty berth, the other RAC ticket holder can then convert the 2 seats into a berth.