Object-oriented programming (OOP) is a programming paradigm that is based on the concept of objects. An object is a self-contained entity that consists of both data and behavior, and can interact with other objects in the program. Objects are defined using classes, which provide a blueprint for creating and manipulating objects.

In OOP, the primary focus is on the objects that make up the program, rather than the procedures and functions that operate on those objects. The program is structured as a collection of objects that communicate with each other through methods and messages.

OOP has a number of advantages:

1. Modularity: Objects are self-contained units of code, which makes it easy to divide a program into smaller, more manageable units.
2. Reusability: Objects can be reused in different parts of a program or in different programs, which helps to reduce code duplication and increase efficiency.
3. Encapsulation: Objects can hide their internal data and behavior from other objects, which helps to protect the integrity of the program and make it easier to maintain.
4. Inheritance: Objects can inherit properties and behaviors from other objects, which allows for code reuse and simplifies the development of new classes.
5. Polymorphism: Objects can be assigned multiple forms or behaviors, which allows for more flexible and adaptable code.

Overall, OOP is a powerful programming paradigm that can help you to write efficient, reusable, and maintainable code. It is particularly well-suited for building large, complex programs and for modeling real-world systems.