What is .NET?
Well, it's another one of those remarkable innovations from the wonderful folks at Microsoft. Having seen their success with "vaporware", they have decided to extend the concept. ("Vaporware" is where MS announces that they will release software, but never do, but it still scares away developers, allowing MS to keep its monopoly.)
Thus .NET is a vapor-concept, intended to scare potential competitors away from anything to do with networking, internet, and distributed clients.
MS has to keep the specifics to a minimum, because the more vague it is, the more threatening it is. Once competitors know the specifics of .NET, they can proceed with initiatives that they feel are not threatened by it.
Of course, MS is also vague about .NET because it doesn't exist, as I've already explained.