Soulstorm said:
What exactly is .NET framework? What does it offer?
It's a big API framework and uses a runtime that works in a way similar to Java. That's a VERY shortened summary, there's plenty of resources out there to fully answer that question better than I can.
Soulstorm said:
Also, is it windows only? I had heard somewhere that it exists for OS X but I'm not sure, and I can't find it anywhere.
The official .NET Framework is Windows only, however, the Mono project have written their own implementation based on the standards that Microsoft published. Mono currently works on Linux, FreeBSD, Mac OS X, Windows and possibly more. Note that Windows Forms is obviously slightly problematic on platforms other than Windows since other operating systems do not have the same window bindings. I haven't followed this progress for a while so you may want to check up what can/can't be done with standard Windows Forms.
You can also use some of the other window bindings, such as Gtk# and Cocoa# that work in a similar way to Windows Forms but the former will only work on machines where GTK is installed and the latter will only work on OS X.
Soulstorm said:
Do I need it to develop sophisticated applications in Windows? How do I get it?
You don't need it to develop applications, however, it's a very nice framework to develop with and it's free.
The traditional approach on the Windows side would be to develop large applications using C++ and more often than not the MFC framework.
The only downside with .NET applications is that you need the .NET framework installed to even run .NET applications.
For more information visit
http://msdn.microsoft.com/netframework/default.aspx and
http://www.mono-project.com/Main_Page.
