Pls Help!

What is it? In the example below the vector toyBox can contain objects of any class derived from Shape, for example, toyBox can contain objects of type Rectangle and Circle. Without polymorphism this would not be possible, toyBox should only be able to contain Shape objects. Explain in a brief paragraph how the toybox vector in the above example knows that an item is either a circle or a rectangle. How could it possible hold two different classes in a vector? How might this be useful