I need more explaination on this topic

Question

thanks

Answer 1

what topic and what language ☺?

Answer 2

Void main() {
int a[]={1,2,9,8,6,3,5,7,8,9};
int *p = a+1;
int *q = a+6;
printf("\n%d",q-p);
}

output : 5
but i need more explanation on it