Object-oriented programming (OOP) is a programming paradigm that uses "objects" to represent data and methods. An object is a self-contained unit that combines both data (attributes) and functions (methods) that operate on that data. This approach allows developers to create modular and reusable code, making it easier to manage complex software systems. In OOP, key concepts include classes, which are blueprints for creating objects, and inheritance, which allows one class to inherit properties and methods from another. Other important principles are encapsulation, which restricts access to certain components, and polymorphism, which enables objects to be treated as instances of their parent class.