Hi NihouPolska,
I may be wrong here, but I think .Net was originally an idea to integrate all aspects of computing in a common framework (network hence .net). At some point Windows 2003 was called Windows.Net too, I believe, as ".Net" was as much a name branding of a future path as anything else.
For programmers it has spawned .Net Framework and C# with VB.Net and C++.Net and an increasing amount of <programming language>.net, ASP.NET and ADO.NET.
You might want to check out Microsoft's own definition (it has a "What is .Net" link)
http://www.microsoft.com/net/
I can't really tell you what it specifically has done to C++ programmers other than to provide C# and C++.Net
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Happy Coding!
Morten Wennevik [C# MVP]