[FissionMailed1]

Well, if you have a "piece", but you want to call move() on that piece, how exactly does that piece move? You wouldn't know how to "move" unless you implemented a specific way to move depending on which type of piece it is (the subclass).

Your last questions are correct. You can choose which make_sound() is called.

Another example of polymorphism, using a function:

Piece* some_piece = new Rook()

move(some_piece*);

void move (piece* piece_to_move) {
// do some stuff to move in a generic way, disregarding which type of piece it is
}

This is all assuming that move() is either virtual or pure virtual.