Microsoft’s programming framework for developers. An environment that provides a new interface to Windows services and the Windows API.
Consists of two main components: The CLR (Common Language Runtime) and the .NET Framework Class Library.
It is composed from a set of programming languages (C#, VB .NET…) that are completely object oriented. The .NET Framework has cross-language compatibility, meaning that .NET components can interact with each other regardless of the language in which they where written.
Advantages of .NET Framework include the reduced time to write code and the efficiency of managing it.
More information at:
MSDN .NET Framework