Web 2.0 emphasizes open data, collective intelligence, and user-generated content. It utilizes technologies like AJAX and asynchronous JavaScript to provide rich user experiences with fewer page refreshes. ASP.NET AJAX is a framework that integrates client-side scripts with ASP.NET to build interactive web applications using techniques like partial page updates without reloading. It aims to increase productivity and provide a clean separation of concerns between content, style, behavior and code.