Apache Struts is an open-source framework used for building web applications in the Java programming language. It follows the Model-View-Controller (MVC) design pattern, which helps separate the application logic from the user interface, making it easier to manage and scale applications. The framework provides a set of tools and libraries that simplify the development process, allowing developers to create dynamic web pages efficiently. With features like form handling, validation, and internationalization, Apache Struts is widely used in enterprise-level applications to enhance productivity and maintainability.