What in Flutter corresponds to the tree hierarchy?

In Flutter, the widget tree hierarchy is represented by the Widget Tree. Each interface element is a widget that can contain other widgets, forming a nested structure.

This widget tree describes the UI structure, and Flutter uses it to build and update the interface. Besides the widget tree, there are also Element Trees and Render Object Trees, which are responsible for the lifecycle and rendering respectively, but the main hierarchy is the widget tree.

An example of a simple widget tree:

Widget build(BuildContext context) {
  return Scaffold(
    appBar: AppBar(title: Text('Example')), // AppBar is a child widget of Scaffold
    body: Center(
      child: Column(
        children: [
          Text('Hello'),
          ElevatedButton(onPressed: () {}, child: Text('Press')),
        ],
      ),
    ),
  );
}