That means this this framework lets you develop native desktop applications for all Windows 10 devices (including PCs, tablet devices, Xbox and mixed reality devices) and macOS ecosystems by only using JavaScript. What it actually does is coordinate React Native support for the Windows 10 SDK and for the macOS 10.13 SDK so that developers don't need to build apps using separate native frameworks or languages. React Native for Windows + macOS is an interesting framework that allows you to build cross-platform desktop applications for both Windows and macOS just by using a single base of React Native code.
What is React Native for Windows + macOS?