Declaration of Null pointer (doubt in the cpp notes of pointers)

#1

in the cpp notes of pointers the null pointer is described as Sometimes it is useful to make our pointers point to nothing. This is called
a null pointer. We assign a pointer a null value by setting it to address 0.

double *p = 0;
But here by doing *p = 0 how to do we set the address of the pointer to 0 ?

#2

u have to set the pointer which is pointing to nothing
if u do int* p;
so it can point so any address
but if u do *p=0/NULL then it is pointing to nothing