confused on what passing by *& is doing!

[voidflux]

Hello everyone...

I'm confused on what exactly is happening when you pass somthing by pointer reference if thats how you say, *&.

For instance here is the function:

//I think this function is suppose to return a valid pointer, pointing to the root after its built

template<typename T> void BuildTree(TreeNode<T>*& root, const string& epxression)
{
	root = NULL;

}

If i had this class:

template<typename T> struct TreeNode
{
   TreeNode(const T& value, TreeNode<T>* left = NULL, TreeNode<T>* right = NULL)
   {
      Value = value;
      Left = left;
      Right = right;
   }

   T Value;
   TreeNode<T>* Left;
   TreeNode<T>* Right;

   bool IsLeaf() const
   {
      return Left == NULL && Right == NULL;
   }

};

WOuld I use the function like this?

//main.cpp
TreeNode<char> *root = new TreeNode<char>;
std::string expression = "a+b*4";

BuildTree(root,expression);

So really my question is, if thats what I should be doing in the main function and also, why is it *& and not just &? or not just *?

Thanks, if you have a website that explains that, that would be helpful as well!