.NOT

Can anyone provide a short, non-marketing-bullshit description of what this steaming pile of shit really is?  Is there ANY reason that a competent developer would ever use it?
http://en.wikipedia.org/wiki/.NET_Framework

.NET is basically

The CLR - Common Language Runtime, the virtual machine that runs

The CIL - Common Intermediate Language, the machine language to which every .NET aware language must compile. The CIL abides to
 
The CTS - Common Type System a standard that specifies how "type definitions and specific values of types are represented in computer memory". Thanks to the CTS we have

The FCL - Framework Class Library, a vast library of types that's available to .NET developers.

Besides all of these, Microsoft created some new languages for .NET, though any language with flexible object semantics can be ported to it. The most popular .NET language is Microsoft's C#, which is basically a less verbose version of Java that isn't stuck in time.