How do pointer to pointers work in C?

Question

How do pointers to pointers work in C? When would you use them?

Answer 1

it's a pointer to the pointer's address value. (that's terrible I know)

basically, it lets you pass a pointer to the value of the address of another pointer, so you can modify where another pointer is pointing from a sub function, like:

void changeptr(int** pp)
{
  *pp=&someval;
}