React Native is Meta's open-source framework for building cross-platform mobile applications using JavaScript and React, enabling developers to write a single codebase that compiles to native iOS and Android apps. Launched in 2015, it has evolved from using an asynchronous JavaScript Bridge to the New Architecture (Fabric, TurboModules, JSI) that delivers native-level performance with synchronous communication. Understanding React Native's component system, navigation patterns, styling with Flexbox, platform-specific APIs, and performance optimization techniques is essential for building production-ready mobile apps that feel truly native while maintaining the speed of web development.