What are the four pillars of Object-Oriented Programming?

The four pillars are: 1) Encapsulation - bundling data and methods, hiding internal state; 2) Abstraction - hiding complexity, exposing only essential features; 3) Inheritance - creating new classes from existing ones, promoting code reuse; 4) Polymorphism - objects of different classes responding to same method differently. These principles help create modular, reusable, and maintainable code. Encapsulation protects data, abstraction simplifies interfaces, inheritance enables hierarchies, and polymorphism allows flexible code.