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 and functions that operate on that data. This approach helps organize code, making it easier to manage and reuse. Key concepts in OOP include classes, objects, inheritance, and polymorphism. In OOP, a class serves as a blueprint for creating objects, defining their properties and behaviors. Inheritance allows one class to inherit attributes and methods from another, promoting code reuse. Polymorphism enables objects to be treated as instances of their parent class, allowing for flexibility in programming.