Flutter is a mobile app SDK developed by Google that allows building high-performance apps for both iOS and Android from a single codebase. It uses the Dart programming language and allows for fast development, an expressive and flexible UI, and native performance. Flutter supports most IDEs and code editors and runs on most platforms. Dart is used to create mission-critical apps for mobile, web, and server environments. Resources for learning Flutter and Dart include codelabs, tutorials, and courses.