React Native is a framework that allows developers to build mobile apps using JavaScript, utilizing the same design principles as React. It provides a rich mobile UI composed of declarative components and supports cross-platform development for both iOS and Android platforms. To start developing with React Native, developers can use tools such as Atom, Nuclide, or Visual Studio Code, which offer features like code completion, debugging, and project management. Additionally, frameworks like Redux, Expo, and Ignite provide additional functionality for building complex applications. Other tools like Flow, ESLint, and Enzyme help with static type checking, code linting, and testing, while Instabug offers performance monitoring and bug reporting capabilities to ensure the stability and quality of mobile apps.