What Exactly a null pointer? and pointer and NULL different or same?

Well Friends, According to the ISO C99 standard: An integer constant expression with value 0, or such an expression cast to type void *, is called null pointer constant. If a null pointer constant is converted to a pointer type, the resulting pointer is called a null pointer ( guaranteed to compare unequal to a pointer to any object or function).

Difference between null pointer and NULL

While null pointer is a pointer which is guaranteed not to point to any object , NULL is just a macro which defines null pointer.