This version of .NET Framework is formerly known as WinFx (Pronounced
as "Win Effects").
Every developer of Microsoft technologies has come across
Win32 Application Programming Interface [API] and the Principle API of all the
Microsoft windows operating systems. But in upcoming versions of Microsoft
Operating Systems, such as Windows Vista, Win32 API will no longer be the
principal API. However, it will continue to be supported; likewise, the old DOS
application can still run under the latest version of operating systems. A new
API called WinFX will replace the Win32 API in upcoming versions of the
Microsoft Windows Operating Systems.
To be clearer, WinFX is the .NET Framework 2.0
with the addition of four specific new technologies as mentioned below:
1) Windows Presentation Foundation
[WPF]
2) Windows Communication Foundation
[WCF]
3) Windows Workflow Foundation [WF]
4) Windows Card Space [WCS]
Figure 1

The above diagram illustrates the pictorial arrangement of
.Net Framework 3.0 [WinFx].
All four new technologies developed are to be used by any
.Net aware/compliance programming language (such as C#.Net, VB.Net, and etc…), which
means all these technologies were developed as managed code/API.
These four new technologies [API's] enable .Net Framework
3.0 developers to develop applications for Windows Operating System by taking
advantage of underlying Windows Operating System features in .Net aware/compliance
programming languages. Hence, developers of .NetFx 3.0 are dealing with Windows
Operating System through Managed API.
So .Net Framework 3.0 [WinFx] = .NetFx 2.0 + WPF +
WWF + WCF + WCS.
My Definition of WinFx - Goes Here…
The Managed Code Programming Model for Upcoming Microsoft
Windows Operating Systems.