Bewildered!!

Hello everyone i am a beginner with C++ and have a very basic grasp of the language! If anyone could help explain the concept of polymorphism, i am having a hard time especially with dynamic polymorphism and the virtual and abstract functions.

Below is a basic program using the virtual function:

Code:

#include<iostream.h>
#include<conio.h>
class c1
{
public:
   virtual  void disp()
    {
      cout<<"hello";
      }
 };
 class c2:public c1
 {
 public:
    void disp()
    {
    cout<<"well";
    }
};
int main()
{
clrscr();
c1 obj;
obj.disp();

getch();
return 0;
}

Declaring classes and getting them to display is understandable, my question is how does the virtual function work in this case? My understanding is that the virtual function stops the second class from inheriting the value of the first class. How does this make the program more effecient? It does not produce any palpable results that i can define. I know that it helps to streamline the runtime right? But beyond that i am flabbergasted! Please if anyone would be so gracious and come to my rescue it would be much appreciated!!

Norman