C++ Language/Objects/Inheritance/PolymorphismSyntax

Frequently, an object is allocated by instantiating the derived class, but "pointed-at" by a pointer variable whose type is "pointer-to-base-class":. If  and   have provided two different implementations of the same   member function, then   would call the base class' implementation. But if the member function had been marked by the  keyword, then   would instead "polymorphically" call the derived class' implementation.

Additional information about polymorphism syntax