React Native is an open-source framework that enables developers to build mobile applications for iOS, Android, and other platforms using JavaScript and React. It allows developers to create native-like apps with a high level of performance while writing most of their codebase in JavaScript, which is familiar to many web developers. By installing the New Relic agent, developers can gain valuable insights into their app's performance, detect crashes, and identify issues that may affect user experience. The agent provides features such as comprehensive performance monitoring, ANR detection and capture, spotting rooted devices, breadcrumbs, service maps, and crash reports, which help teams make data-backed decisions to improve the speed and UX of their apps.