Alright so pointers

I have a question about pointers: when will you ever need a pointer to a pointer?  No seriously, when do you ever need the address of a pointer?  And this isn't one of those "COME AT ME BRO" threads, I am honestly curious, when?

When Jewish girls menstruate for the first time, their mothers often slap them across the face, a cultural tradition thought by some to signify the difficulties of life as a woman.