The .NET Framework is a popular development platform for building apps for Windows, Windows Store, Windows Phone, Windows Server, and Windows Azure. The .NET Framework platform includes
programming languages like c#,vb,etc
Technologies like Asp.net
Databases like sql server
Asp.Net is a technology developed by Micro soft for the development of distributed applications.
Microsoft started development of the .NET Framework in the late 1990s, originally under the name of Next Generation Windows Services (NGWS). By late 2000 the first beta versions of .NET 1.0 were released.
Because computer systems commonly require interaction between newer and older applications, the .NET Framework provides means to access functionality implemented in newer and older programs that execute outside the .NET environment. Access to COM components is provided in the System.Runtime.InteropServices and System.EnterpriseServices namespaces of the framework; access to other functionality is achieved using the P/Invoke feature.
Common Language Runtime engine
The Common Language Runtime (CLR) serves as the execution engine of the .NET Framework. All .NET programs execute under the supervision of the CLR, guaranteeing certain properties and behaviors in the areas of memory management, security, and exception handling.
The Base Class Library is a part of the Framework Class Library, it's functionality available to all languages using the .NET Framework. The BCL provides classes that encapsulate a number of common functions, including file reading and writing, graphic rendering, database interaction, XML document manipulation, and so on.
The .NET Framework includes design features and tools which help manage the installation of computer software to ensure it does not interfere with previously installed software, and it conforms to security requirements.
Additionally, .NET provides a common security model for all applications.
While Microsoft has never implemented the full framework on any system except Microsoft Windows, it has engineered the framework to be platform-agnostic, and cross-platform implementations are available for other operating systems. Microsoft submitted the specifications for the Common Language Infrastructure. the C# language, and the C++/CLI language to both ECMAand the ISO, making them available as official standards. This makes it possible for third parties to create compatible implementations of the framework and its languages on other platforms