PHP frameworks are pre-built collections of code that help developers create web applications more efficiently. They provide a structured way to build applications by offering reusable components, libraries, and tools, which can save time and reduce errors. Popular frameworks include Laravel, Symfony, and CodeIgniter. Using a PHP framework allows developers to follow best practices and design patterns, making their code more organized and maintainable. Frameworks often come with built-in features like routing, authentication, and database management, which streamline the development process and enhance the overall performance of web applications.