Polymorphism explained. Differences?

Polymorphism: Why is it needed especially from an OOP standpoint? What is the essential concept when you cast objects regarding Polymorphism/Inheritance? (Related Chapters 11,12,13, 19) Generics: Explain Generic Programming. Why is generics important as a data type regarding objects? Polymorphism and Objects: Explain an array of polymorphic objects in a single/double dimensional array. How do you access this? How do you process this? When would you use this?    Also, when the new topic/chapter is posted regarding File/IO: Write a few lines of code that allow you to save/retrieve this data from a file using the appropriate class/methods. Do this in two ways: StreamFile I/O and URL access. You can also illustrate this in your code via text (.txt) and binary (.dat) data access.  Also, write a few more additional lines of code illustrating StreamFile  I/O access for .txt and .bin files.

Overloading entails what, exactly? What makes it unique from other forms of influence, like coercion or polymorphism, and how does it operate?

What is Polymorphism? Explain its relation to Inheritance and Generic Programming.