VB.Net / C# provide polymorphism through the following mechanisms:

1. Inheritance -- base class provides overridable methods which are re-implemented in derived classes.
2. Interface -- different class can implement same interface resulting in different implementations of interface methods.
3. Virtual methods -- achieve runtime polymorphism.

VB.Net achieves polymorphism thru
1. Overriding
2. Overloading

Polymorphism refers to an object taking different shapes in its life time . It is linked to inheritance .

Thru overloading the same method works with different parameters

eg : public void area(int parameter1)
{

areavalue parameter1 * parameter1;

}

public void area(int parameter1 int parameter2)
{
areavalue parameter1*parameter2;
}

Overiding : we override the methods in the abstract class. Overriding is the process by which a method in the parent class is replaced by the derived class.

public override void square();