What is the difference between X,I & J classes in indian airlines?

Question

It was printed on my boarding pass that I belonged to "i" class.
The next person to me in my flight had class "X" printed.
If we blonged to different classes, why did we land up in the same cabin?

Answer 1

They are ifferent fares, some are non-refundable.
Basically it depends on the price.

Answer 2

Its just a simple way of classification. Not on the basis of quality of travel. Its done randomly.