It's the first version of .NET that's cross-platform, it's the first version of .NET that's totally open source, and it's the first version of .NET that can build self-contained apps (no need to have .NET Framework installed to run .NET Core 1.0 apps). See the release notes[0] for more info.
It's called "core", because it doesn't contain the Windows desktop UI toolkits, like Windows Forms and Windows Presentation Foundation (WPF), and excludes some other Windows-specific functionality.
Additionally, this is the first version of .NET in which apps can be totally self-contained. Previously, you'd need to install the .NET Framework on your machine to run .NET apps. That is no longer a requirement in .NET Core 1.0.
So, it's a pretty huge release. And really the first time in decades that MS has built it's premier dev stack with multiple OS support.
>> "I tried it - it puts 50MB of DLLs beside HelloWorld"
That's a bad test for a framework. It's like saying, "I bought an $80,000 car to drive to my neighbor's house across the street - I could have just walked!"
A good test is, "What is the full install size of a real app built on .NET Core?"
And the answer is, not much larger than any other app. All that code has to live somewhere, either in your app or in your libraries.
Mono supports COM interop on Linux, too. At its most basic level, COM is really just an ABI, and there's nothing Windows-specific about it (see also: XPCOM).
It's called "core", because it doesn't contain the Windows desktop UI toolkits, like Windows Forms and Windows Presentation Foundation (WPF), and excludes some other Windows-specific functionality.
Additionally, this is the first version of .NET in which apps can be totally self-contained. Previously, you'd need to install the .NET Framework on your machine to run .NET apps. That is no longer a requirement in .NET Core 1.0.
So, it's a pretty huge release. And really the first time in decades that MS has built it's premier dev stack with multiple OS support.
[0]: https://github.com/dotnet/core/blob/master/release-notes/1.0...