The .NET Core is a set of runtime, library and compiler components that allow you to create apps that run on Windows, Mac OS X and Linux. It can be installed locally with your app with only the packages you need. It provides a lightweight development model and the flexibility to work with your favorite development tools on your favorite development platform.
.NET Core supports Windows, Linux, OS X, and Docker platforms.
.NET Core is a modern, module, adaptable, managed, interoperable, cross-platform, extensible, and open platform that allows developers to build Windows, Linux, and Mac based applications, components, and services.
.NET Core Preview 1 is available to download here:
https://www.microsoft.com/net/core
The preview 1 version of .NET Core supports Console Applications and Web Applications only. Learn more about .NET Core and get started here:
http://dotnet.github.io/docs/