.NET Framework and versions

To check versions of .NET framework installed on a machine to go  Start > Run and type in regedit.exe

To find .NET Framework versions by viewing the registry (.NET Framework 1-4)

1. On the Start menu, choose Run.
2. In the Open box, enter regedit.exe.
   You must have administrative credentials to run regedit.exe.
3. In the Registry Editor, open the following subkey:
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP

.NET 4.6 comes with Visual Studio 2015

.NET Framework is:

A programming infrastructure created by Microsoft for building, deploying, and running applications and services that use .NET technologies, such as desktop applications and Web services. The .NET Framework contains three major parts: the Common Language Runtime. the Framework Class Library. ASP.NET.