Passing a string literal as a function parameter defined as a pointer

I am reading the chapter on arrays and pointers in Kernighan and Richie's The C Programming Language.

They give the example:

/* strlen:  return length of string s */
int strlen(char *s)
{
    int n;

    for (n = 0; *s != '\0'; s++)
        n++;
    return n;
}

And then say:

“Since s is a pointer, incrementing it is perfectly legal; s++ has no effect on the character string in the function that called strlen, but merely increments strlen’s private copy of the pointer. That means that calls like

strlen("hello, world");  /* string constant */
strlen(array);           /* char array[100]; */
strlen(ptr);             /* char *ptr; */

all work.”

I feel like I understand all of this except the first call example: Why, or how, is the string literal "hello, world" treated as a char *s? How is this a pointer? Does the function assign this string literal as the value of its local variable *s and then use s as the array name/pointer?