Flutter is an open-source mobile app development framework created by Google that allows building Android and iOS apps using one codebase and programming language, Dart. The document discusses Flutter and Firebase, describing Flutter as a framework that offers hot reloading and reusable widgets. Firebase is presented as a real-time database and backend tool that provides a serverless alternative to writing custom backend code, saving development time and costs. Key features of Firebase mentioned are authentication, cost savings over custom backends, and machine learning capabilities.