The .NET Framework has two main components: the common
language runtime and the .NET Framework class library.

You can think of the runtime as an agent that manages code
at execution time, providing core services such as memory
management, thread management, and remoting, while also
enforcing strict type safety and other forms of code
accuracy that ensure security and robustness.

The class library, is a comprehensive, object-oriented
collection of reusable types that you can use to develop
applications ranging from traditional command-line or
graphical user interface (GUI) applications to applications
based on the latest innovations provided by ASP.NET, such as
Web Forms and XML Web services.