What is Dangling Pointer

A dangling pointer points to memory that has already been de-allocated or freed. Accessing that pointer might cause a Segmentation fault.
For Example
#include
int main(void)
{
    int *ptr1,*ptr2;
    ptr1 = malloc(sizeof(int));
    ptr2=ptr1;
    *ptr1 = 3;
    free(ptr1);    // memory released
    printf(“%d”,*ptr2); // trying to access the freed memory
    return 0;
}
Trying to access the freed memory leads to dangling pointer.