Flutter is not a programming language, it is a software development kit (SDK) with prewritten code, containing ready-to-use and customizable widgets, along with libraries, tools, and documentation that together help to develop cross-platform apps. Flutter’s language for cross-platform development is Dart, which was built by Google. Flutter avoids using a bridge to connect with the native layer (such as Android or iOS). This reduces performance issues and increases app startup time.
Obviously, Flutter having its own programming language means that to get your app developed, you’ll require developers to code in Dart. However, Dart is pretty similar to Java, .Net, Kotlin, Swift, or JavaScript and it’s comparatively easy to learn.