ASP.NET allows for simplified and modular web development through features like server-side coding, rich web forms, drag-and-drop design, and reusable server controls. The page lifecycle in ASP.NET involves events like init, load, and render that occur on both the client and server sides. State management is provided through view state stored on the client and session/application state stored on the server. Master pages allow content to be templated for reuse across pages. A web application project compiles all pages into a single DLL for improved performance compared to a web site project.