Can anyone help me to understand this function?
CheckList(Listfile*& Listitems,bool showSortList)
Listfile is a class but I can't understand what is Listfile*&, what would be return to Listitems? 
It's a reference to a pointer:
CheckList(Listfile*& Listitems,bool showSortList)
          ^^^^^^^^^ pointer to Listfile
                   ^ reference
you should study C++ better, this can be found in any decent C++ book.
Its taking reference of pointer to Listfile. Have a look here for detail of this topic:
http://www.codeproject.com/Articles/4894/Pointer-to-Pointer-and-Reference-to-Pointer
 
    
    