Its the first non-preview release of the product called ".NET Core"; it is, therefore, versioned as ".NET Core 1.0".
This is a different (but related) product to the .NET Framework (current version, 4.6) -- future versions of the .NET Framework will be built on top of .NET Core, which will be updated more frequently than the larger Framework. So, maybe .NET Framework 5.0 will be built on something like .NET Core 1.3 -- or 2.0, whatever.
This is a different (but related) product to the .NET Framework (current version, 4.6) -- future versions of the .NET Framework will be built on top of .NET Core, which will be updated more frequently than the larger Framework. So, maybe .NET Framework 5.0 will be built on something like .NET Core 1.3 -- or 2.0, whatever.