CoreFX is the foundational class libraries for .NET Core. It includes types for collections, file systems, console, JSON, XML, async and many others.
Build cross platform desktop apps with ASP.NET Core.
CoreCLR is the runtime for .NET Core. It includes the garbage collector, JIT compiler, primitive data types and low-level classes.
[Archived] ASP.NET Core MVC is a model view controller framework for building dynamic web sites with clean separation of concerns, including the merged MVC, Web API, and Web Pages w/ Razor. Project moved to https://github.com/aspnet/AspNetCore