what is polymorphism and how can I use it

in this situation?
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Book is the root class Nativebool and ForeignBook derivated from it.

you want to enter a number from user.
if number is 1, you will create NativeBook object
else if number is 2, you will create ForeignBook Object; (Polymorphism)

int main()
{
Book *fptr; // you will point a object prefered by user
……………………………………………….
NativeBook tf(“xxx”,”xxx”,”1997”,60);
(1) tf.display();
ForeignBook ff(“Brave”,”Michael Michiel”,”2002”,95,”English”);
(2) ff.display();
Cout<<”please give a number
(1) Native Book
(2) Foreign Book”;
// You will code this area..
………………………………..
fptr=&ff; // if you enter 1 polymorphism
(3) fptr->display(); //
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foreignbook ff, behave like nativebook bf. How can I do this in this situation.

I talk about polymorphism towards the middle/end of the big post

thanks