Where is the Expanded widget used in Flutter?

Expanded is used inside widgets like Row, Column, or Flex to make a child widget occupy the maximum available space in the main axis. It is useful for creating responsive interfaces and evenly distributing widgets. For example, to create a row with two buttons, one of which fills the remaining space.

Row(
  children: <Widget>[
    Container(
      color: Colors.red,
      width: 100,
    ),
    Expanded( // This widget will fill the remaining space
      child: Container(
        color: Colors.blue,
      ),
    ),
  ],
)