.NET is a set of Microsoft software technologies designed to facilitate the development and execution of large, interoperable Web-based, desktop, distributed, and server applications, both for e-commerce and global electronic businesses. .NET is the Microsoft solution for Web services. Like other Web service environments, it relies heavily on eXtensible Markup Language (XML) and SOAP.
.NET has been incorporated across Microsoft's clients, servers, services, and tools. For developers, .NET is manifested in the programming model delivered in the Microsoft .NET Framework. .NET is based on the reuse of services. Microsoft defines services as small, discrete, building-block applications that connect to each other as well as to other, larger applications via the Internet or an intranet.
.NET supports many different programming languages. Normally .NET applications are compiled into Microsoft intermediate language (MSIL) and run in a sort of virtual operating system, the CLR. The compiled code is called managed code, because it is managed by the CLR.
Applications compiled in other languages can also run in .NET environments under the Windows operating system, and Microsoft has provided many facilities to allow such programs to interoperate with managed code.