Polymorphism

The real power of object orientation goes beyond classes and encapsulation. A well-designed OO program can manage many types of data. When well-designed classes encapsulate specific details of objects into the appropriate places, something curious happens: the code often becomes less specific. Moving the details of what the program knows about individual Cats (the attributes) and what the program knows that Cats can do (the methods) into the Cat class means that code that deals with Cat instances can happily ignore how Cat does what it does.