- .NET Building Block Services, or programmatic access to certain services, such as file storage, calendar, and Passport.NET (an identity verification service).
- .NET device software, which will run on new Internet devices.
- The .NET user experience, which includes such features as the natural interface, information agents, and smart tags, a technology that automates hyperlinks to information related to words and phrases in user-created documents.
- The .NET infrastructure, which comprises the .NET Framework, Microsoft Visual Studio.NET, the .NET Enterprise Servers, and Microsoft Windows.NET.
The .NET infrastructure is the part of .NET that most developers are referring to when they refer to .NET. You can assume that any time I refer to .NET (without a preceding adjective) I'm talking about the .NET infrastructure. The .NET infrastructure refers to all the technologies that make up the new environment for creating and running robust, scalable, distributed applications. The part of .NET that lets us develop these applications is the .NET Framework.
The .NET Framework consists of the Common Language Runtime (CLR) and the .NET Framework class libraries, sometimes called the Base Class Library (BCL). Think of the CLR as the virtual machine in which .NET applications function. All .NET languages have the .NET Framework class libraries at their disposal. If you're familiar with either the Microsoft Foundation Classes (MFC) or Borland's Object Windows Library (OWL), you're already familiar with class libraries. The .NET Framework class libraries include support for everything from file I/O and database I/O to XML and SOAP. In fact, the .NET Framework class libraries are so vast that it would easily take a book just to give a superficial overview of all the supported classes.
As a side note (as well as an admission of my age), when I use the term "virtual machine," I don't mean the Java Virtual Machine (JVM). I'm actually using the traditional definition of the term. Several decades ago, before Java was anything more than another word for a dark, hot beverage, IBM first coined "virtual machine." A virtual machine was a high-level operating system abstraction within which other operating systems could function in a completely encapsulated environment. When I refer to the CLR as a kind of virtual machine, I'm referring to the fact that the code that runs within the CLR runs in an encapsulated and managed environment, separate from other processes on the machine.