Object-oriented programming (OOP) is a programming paradigm that uses "objects" to represent data and methods. An object is an instance of a class, which is a blueprint that defines the properties and behaviors of that object. OOP promotes code reusability and organization by allowing developers to create modular code that can be easily maintained and extended. Key concepts of OOP include encapsulation, inheritance, and polymorphism. Encapsulation involves bundling data and methods that operate on that data within a single unit, or object. Inheritance allows one class to inherit properties and methods from another, promoting code reuse. Polymorphism enables objects to be treated as instances of their parent class, allowing for flexible and dynamic code execution.