Flutter is an open-source SDK developed by Google for cross-platform app development, designed to streamline the process and meet the growing demand for mobile technology. It offers features such as a single codebase for both iOS and Android, hot reload for efficient development, and a wide range of customizable widgets, making it a preferred choice among developers. As a rapidly evolving framework, Flutter is expanding beyond mobile to desktop and web applications, positioning itself as a reliable solution for startups and tech enterprises.