@angelplusultra
Distinct() keeps the first instance of an element and discards the rest.

The reason we reverse is because we want to keep the last item, not the first. A requirement from the kata description: "keeping the last ( rightmost ) occurrence of each element"

So we reverse it, remove the duplicates, then reverse it again to get it back to the original order.

Why are you reversing the array in the first place?

it returns only uniqie elements.
So if you have numbers 1,2,3,5,4,1,2,3 your solution would be 5,4,1,2,3.
Method Reverse makes this array look like 3,2,1,4,5,3,2,1. Then method Distinct removes duplicates (second and all further duplicates), so we have it like 3,2,1,4,5. And next reverse returns an answer 5,4,1,2,3

What is Distinct?