The .NET Framework is a software platform that allows developers to write and run applications and web services in any compliant language. It provides a common language runtime and class libraries. Applications are compiled to an intermediate language (IL) that is then compiled to native machine code by the common language runtime (CLR). The CLR handles memory management, security, and other low-level tasks. The .NET Framework supports multiple programming languages and tools like Visual Studio. It allows building Windows forms applications, web applications with ASP.NET, and web services.