The Microsoft .NET architecture is the programming model for the .NET platform. The .NET Framework provides a managed execution environment, simplified development and deployment and integration with a wide variety of programming languages.
The .NET Framework has two key parts:
The .NET Framework class library is a comprehensive, object-oriented collection of reusable types that you can use to develop applications. The .NET Framework class library includes ADO.NET, ASP.NET, and Windows Forms.
The common language runtime (CLR) is the core runtime engine for executing applications in the .NET Framework. You can think of the CLR as a safe area - a "sandbox" - inside of which your .NET code runs. Code that runs in the CLR is called managed code. It is fully protected from the outside environment and highly optimized within, taking advantage of the services that the CLR provides such as security, performance, deployment facilities, and memory management, including garbage collection.