.NET Core gives you a blazing fast and modular development platform for creating .NET applications that run on Windows, Linux and Mac. Cross-platform and open source, .NET Core provides a light weight development model and the flexibility to work with your favorite development tools on your favorite development platform.
The Release Candidate is now available for .NET Core 2.1 with a "go-live" license. This means you can use this release in production and Microsoft will support you. .NET Core 2.1 RC includes ASP.NET Core for web applications and Entity Framework Core for data. New features include support for realtime web communication with SignalR, numerous improvements in the web and data stacks, improved compatibility with .NET Framework, performance improvements, and tooling support in Visual Studio 2017 15.7.
Source: Azure Roadmap