The .NET framework is a software framework developed by Microsoft that runs primarily on Windows. It includes a common language runtime (CLR) that manages the execution of .NET programs. Source code is compiled to an intermediate language (CIL/MSIL) and executed by the CLR on the local machine. The .NET framework also includes a large class library (FCL) that provides useful functionality for developing applications. .NET Core is an open-source version of .NET that runs on Windows, Linux and macOS. It includes a subset of the FCL but allows for cross-platform deployment of .NET applications. The .NET Standard defines a common set of APIs that can be consistently implemented on different .NET platforms.