pointers - c++ *& dereference address of operator?

Question

In a recent assignment for a data structures class, we we're expected to use this "*&" in a function parameters list. I am having trouble finding info on why this exists, and even what it does. Is it standard practice to use this?

Here's a code snippet

template <class T>
Thing <T> * action(const T &dataIn, Thing <T> *& thingIn)
{
    if(thingIn == NULL)
    {
        Node <T> *newThing = new Thing <T> (dataIn);

        newThing->ptr = thingIn;
        thingIn= newThing ;

        return(newThing );
    }
}

I guess another part of my question is, why use "*&" at all couldn't you just send the pointer?

Answer 1

It is used for a reference type pointing to a pointer

Example

int *&ref = ptr;

in the above example, ref is a reference to an int pointer ptr

which then can be passed in to a function

function(int *&ref)