Object-oriented programming, or OOP, is a paradigm that structures software design around objects, which can be thought of as real-world entities. These objects contain both data (often referred to as properties or attributes) and behavior (functions, referred to as methods). The primary goal of OOP is to promote reusability, modularity, and organization in software development. It achieves this through several key concepts: encapsulation, inheritance, and polymorphism. Encapsulation refers to bundling the data and methods that operate on that data within a single unit, or object, and restricting access to some of the object’s components to protect the internal state from outside interference. Inheritance allows a class to inherit properties and methods from another class, promoting code reuse. Polymorphism enables objects of different classes to be treated as instances of the same class through a shared interface, allowing for flexible and interchangeable code components. Languages like Java, C++, Python, and Ruby are known for supporting OOP principles. For example, in a simple application where you're managing a library system, a `Book` class might encapsulate properties like `title` and `author` and methods like `borrow()` and `return()`. OOP allows you to create instances of this `Book` class and manipulate them without needing to duplicate code for each individual book. Furthermore, you could create a subclass `Ebook` that inherits from `Book` but also adds new methods like `download()`. One of the advantages of OOP is that it encourages developers to think in terms of objects and their interactions, making complex programs more understandable. However, it’s important to recognize that OOP is not the only paradigm, and in certain cases, other approaches like functional programming may be more suitable.