Struts is an open-source framework used for building Java web applications based on the Model-View-Controller (MVC) architectural pattern. It provides a set of reusable components and utilities that help developers create scalable, maintainable, and flexible web applications.

Key components of the Struts framework:

1. Model: The model represents the data and business logic of the application. It typically consists of JavaBeans or POJOs (Plain Old Java Objects) that hold the application’s data and the business logic that operates on this data.

2. View: The view is responsible for rendering the user interface and presenting the data to the end-users. In Struts, the view is usually implemented using JavaServer Pages (JSP) or HTML templates.

3. Controller: The controller manages the flow of the application and acts as an intermediary between the model and the view. It receives user requests, processes them, interacts with the model to retrieve or manipulate data, and finally, selects the appropriate view to render the response.

4. Actions: Actions are Java classes that handle user requests and form the core of the controller. They process incoming requests, interact with the model to perform necessary actions, and forward the results to the appropriate view.

5. Configuration: Struts uses configuration files (usually XML-based) to define the mapping between incoming URLs and corresponding action classes, view templates, etc. These configuration files help in controlling the flow of the application and allow developers to change the behavior of the application without modifying the code.

6. Tag Libraries: Struts provides custom tag libraries that allow developers to encapsulate the presentation logic and easily generate HTML or other types of responses. This makes it simpler to create dynamic web pages without mixing Java code with the presentation layer.