Microsoft ASP.NET Core is a brand new cross-platform ASP.NET product from Microsoft.
ASP.NET Core 1.0 has many features for developers, including a few of these below taken from the Microsoft .NET Blog
NET Core is composed of the following parts:
A ASP.NET runtime, which provides a type system, assembly loading, a garbage collector, native interop and other basic services.
A set of framework libraries, which provide primitive data types, app composition types and fundamental utilities.
A set of SDK tools and language compilers that enable the base developer experience, available in the .NET Core SDK.
The ‘dotnet’ app host, which is used to launch .NET Core apps. It selects and hosts the runtime, provides an assembly loading policy and launches the app. The same host is also used to launch SDK tools in the same way.