Flutter is an open-source UI toolkit from Google for crafting beautiful, natively compiled applications for desktop, web, and mobile from a single codebase. Flutter apps are built using the Dart programming language.
Widgets are basically the UI components in Flutter. There are 2 types of widgets in flutter. Stateless and StateFul.
This is a object orieanted programming language which is used to write flutter code. Dart allows Flutter to avoid the need for a separate declarative layout language like JSX or XML. It uses AOT compilation to make the code run faster on host device.