Struts 2.0 is an open source MVC framework that makes building web applications with Java easier. It uses the Model 2 architecture pattern with actions as controllers, models to handle business logic, and JSPs as views. Struts handles common tasks like request processing, validation, and forwarding so developers can focus on business logic. While simple applications can use just servlets and JSPs, larger ones benefit from Struts' standardized structure, tags, and features which reduce complexity and improve maintenance.