Facebooks' React Native is a framework for building cross-platform apps in Javascript components. It offers developers increased development speeds with hot-reloading and cross-platform support. Under the hood, that translates the code into to real native components, which means it is fast and has a premium feel.
Like Googles' Flutter, we're hearing many teams say good things about React Native. It's got a growing community and there are many open source components available.
As with any cross-platform framework, it can reduce development costs and timescales if the team are invested in it. It is a good choice for apps that are under continual development, where the many dependencies can be updated regularly.