Polymorphism is a fundamental concept in object-oriented programming that allows objects of different classes to be treated as objects of a common superclass or interface. It enables a single interface or method to be used for objects of various types, providing flexibility and code reusability.

There are two main types of polymorphism:

1. Compile-time Polymorphism (Static Polymorphism): Also known as method overloading or function overloading, it allows multiple methods with the same name but different parameters to coexist in a class. The appropriate method is determined at compile-time based on the number, types, and order of the arguments provided.
2. Runtime Polymorphism (Dynamic Polymorphism): Also known as method overriding, it occurs when a subclass provides its own implementation of a method that is already defined in its superclass. The appropriate method to be executed is determined at runtime based on the actual object type rather than the reference type.

Polymorphism allows objects to exhibit different behaviors depending on their specific types, while still adhering to a common interface. It promotes code flexibility, extensibility, and modularity, as it enables the interchangeability and interoperability of objects of different classes or subclasses.

Overall, polymorphism is a powerful concept that allows for more modular and flexible code design, promoting code reuse and simplifying the handling of objects with similar behaviors but different underlying implementations.