Object-oriented programming (OOP) is a programming paradigm centered around objects and classes. The key principles of OOP are encapsulation, inheritance, polymorphism, and abstraction.

Encapsulation involves bundling data and methods that operate on the data within a single unit, typically a class. This principle hides the internal state of objects and only exposes necessary components, promoting modularity and reducing complexity.

Inheritance allows a new class, known as a subclass, to inherit attributes and behaviors (methods) from an existing class, called a superclass. This promotes code reuse and establishes a natural hierarchy, making systems easier to manage and extend.

Polymorphism enables objects to be treated as instances of their parent class rather than their actual class. This allows methods to be written that can operate on objects of different classes, enhancing flexibility and maintainability. Polymorphism is often achieved through method overriding and overloading.

Abstraction focuses on exposing only the essential features of an object while hiding the complex implementation details. This simplifies interaction with objects and reduces code complexity by allowing programmers to focus on high-level functionality.

Together, these principles facilitate the creation of modular, reusable, and maintainable code, making OOP a powerful approach for software development.