Displaying list horizontally

I recently came across this geeksforgeeks program of Hashing with separate chaining: https://ide.geeksforgeeks.org/WqMyTHiyA3

But I am unable to understand it's code for displayHash() member function.

My questions are:

1)Is there really a need for using auto type (as code works fine with int type too)?

2)How is list being displayed horizontally using auto x:table[i](syntax not clear to me)?