What is significance of ** here?

Question

I was learning pointer but not understand the this program?
#include <stdio.h>
int main(){
int x=10;
int *ptr=&x;
int **ptr1=&ptr;

printf("%d\n",x);
printf("%u\n",&x);
printf("%u\n",ptr);
printf("%d\n",*ptr);
printf("%u\n",**ptr1);
printf("%u\n",ptr1);

return 0;
}

Answer 1

Double pointer (pointer that points to another pointer)

https://www.tutorialspoint.com/cprogramming/c_pointer_to_pointer.htm
https://www.tutorialspoint.com/double-pointer-pointer-to-pointer-in-c