In Indian Railways, 3A stands for AC 3-Tier, which is the most preferred category of train-tickets for traveling as they provide a fairly good experience at an affordable price. It has 8 berths in each compartment. On the other hand, 3E stands for 3rd AC Economy, which is a very rare AC 3 tier Economy class available in some Duronto trains and Garib Rath Express. It has 9 berths per compartment, with 3 side berths making it different from 3A. Therefore, the key difference between 3E and 3A is the number of berths per compartment and the arrangement of side berths.