Object-Oriented Programming (OOP) is a programming paradigm that organizes software design around objects, which are instances of classes. It is based on four main principles: Encapsulation, Inheritance, Polymorphism, and Abstraction. Encapsulation means wrapping data and methods into a single unit (class) while hiding internal details using access modifiers. Inheritance allows a class to inherit properties and behaviors from another class, promoting code reusability. Polymorphism enables a single function or method to behave differently based on the context, either through method overloading (compile-time) or method overriding (run-time). Abstraction focuses on exposing only essential features of an object while hiding the complex implementation. Together, these principles make the code more modular, maintainable, and scalable.