An ASP.Net Webforms & MVC developer designs, codes, tests, and manages dynamic websites and applications using ASP.Net Webforms and Model-View-Controller (MVC) framework. They create webforms, which are server-side files written in a .Net language, to handle user interactions and server responses. With MVC, they divide applications into three interconnected parts: Model (data), View (user interface), and Controller (processes commands), to provide a clean separation of concerns. They also develop and maintain databases, ensure security and data privacy, troubleshoot and debug applications, collaborate with frontend developers, and work to improve application performance and responsiveness.