This document discusses building cross-platform native mobile apps using JavaScript. It defines what a native mobile app is and outlines challenges with building apps for multiple platforms, such as iOS and Android. It then introduces approaches for building cross-platform apps using JavaScript, including frameworks like Titanium, React Native, and NativeScript that allow coding apps in JS while maintaining native UIs. Benefits include writing code once that runs on different platforms, along with faster development times and lower costs compared to building platform-specific apps.