Why does scanf() need & operator (address-of) in some cases, and not others?

Question

Why do we need to put a & operator in scanf() for storing values in an integer array but not while storing a string in a char array?

Answer 1

scanf("%d", a + i ) works too.

%d and %s just tell scanf what to expect but in both cases it expects an address

in C, arrays and pointers are related.

%s just says to scanf to expect a string which is \0 terminated, whether it will fit into the character array or not scanf doesn't care.