.NET framework is a software platform that supports the development of web and Windows applications, emphasizing a shift from client-centric to server-centric development. It features a common language runtime (CLR) for multiple programming languages, improved performance through caching, and offers services including ASP.NET for web applications and ADO.NET for data access. The document contrasts .NET with J2EE, highlighting differences in execution engines, cross-platform capabilities, and language support.