Symfony is a popular open-source web application framework written in PHP. It provides a set of reusable components and tools that help developers build robust and scalable web applications efficiently. By following the Model-View-Controller (MVC) architecture, Symfony promotes a clear separation of concerns, making it easier to manage and maintain code. One of the key features of Symfony is its flexibility, allowing developers to use only the components they need for their projects. It also has a strong community and extensive documentation, which support developers in learning and implementing best practices. This makes Symfony a preferred choice for many web development projects.