.NET is a cross-platform runtime and libraries, for cloud, IoT and desktop apps. It includes a garbage collector, JIT compiler, primitive data types and class libraries.
This repo contains the .NET Core runtime, called CoreCLR, and the base library, called mscorlib. It includes the garbage collector, JIT compiler, base .NET data types and many low-level classes.
This repo contains the .NET Core foundational libraries, called CoreFX. It includes classes for collections, file systems, console, XML, async and many others.
This repo contains CoreRT, a .NET Core runtime optimized for AOT (ahead of time compilation) scenarios, with the accompanying .NET Native compiler toolchain.