.NET is one of the platforms provided by Microsoft, which is used to build a variety of applications using Windows.
The ability to develop classes, libraries, and APIs and run, debug, and deploy code onto web services and applications form are the key uses of this framework. It supports a lot of languages, and you can work with everything from C# to VB all the way to Perl, and more.
The object-oriented model is championed here in the .NET framework