Using references as control variable in range-based for loops in c++

I have been messing with range-based for loops, like this one:

int a[] = {1, 2, 3, 4};

for(auto i : a){
    cout << i;
}

(Correct me here if I'm wrong)I suppose that i assigned at start of every iteration with the next value in sequence container a like:

i = a[0] … iteration 1

i = a[1] … iteration 2

…

i = a[9] … iteration 10

I wanted to ask how does this works when loop control variable is a reference:

for(int &i : a){...}

Since a reference is not assigned at initialization but binded, and the binding never changes then how does i iterates through a saving value of an element of a in a given iteration but when a reference is assigned except in the declaration it is like assigning the original variable. To change array elements we have to use reference, my question is how a single reference can be binded to different variables(i.e. elements of a during looping) as every element can be modified with the same reference variable inside the loop.

Thanks