Polymorphism in Java enables treating objects of different types uniformly through a common interface or superclass. A parent reference can hold child objects: 'Animal animal = new Dog();'. The actual object's methods are called at runtime (dynamic dispatch). This enables writing code that works with any subtype: a method accepting 'Animal' works with any animal type. Understanding polymorphism is fundamental to flexible, extensible designs and is a core OOP principle.

Mastering polymorphism enables you to write flexible, extensible code. Being able to work with types generically while getting specialized behavior is central to OOP benefits. In professional development, polymorphism appears in plugin systems, strategy patterns, and extensible frameworks. For example, a drawing program with a 'Shape' interface can work with any shape type polymorphically: 'for(Shape shape : shapes) shape.draw();'. Adding new shapes requires no changes to drawing code.

By learning polymorphism thoroughly, you'll design flexible, maintainable systems. Understanding that method calls are resolved at runtime (late binding) helps you leverage polymorphism effectively. This knowledge is fundamental to OOP design. Prerequisites include understanding inheritance, interfaces, and method overriding.