Berth codes and train classes: LB, MB, UB, SL, SU and 1A to 2S

The short answer

LB, MB and UB are lower, middle and upper berths. SL and SU are side lower and side upper. Classes run from 1A (AC First Class) and 2A (AC two-tier) to 3A (AC three-tier), 3E (AC three-tier economy), SL (sleeper, non-AC), CC (AC chair car) and 2S (second sitting). Senior citizens and women aged 45 and above can be allotted lower berths where available.