The .NET Framework includes two main components: the common language runtime and the .NET Framework class library. The common language runtime is the foundation of the .NET Framework. The runtime is common to three languages: Visual Basic, JScript, and C# (pronounced "C Sharp"). The common language runtime manages the code at execution time. It does the memory management, thread management, and runs the code on different platforms (client or server). It enforces strict variable type definitions, security, and robustness. For example, the runtime automatically manages references to objects, releasing them when they are no longer being used. This automatic memory management resolves the two most common C++ application errors, memory leaks and invalid memory references. The runtime can be hosted by both client applications (Internet Explorer), as well as server applications (Microsoft SQL Server, IIS, ASP.NET). The runtime also accelerates developer productivity. Programmers can write applications in their development language of choice (JScript, of course), yet take full advantage of the class library and components written in other languages by other developers. Current hosts (such as ASP.NET) provide a wealth of reusable components that are ready to be used.
To learn more on JScript .NET, go to Column 107, JScript .NET, Part I: The Mechanics.