Container with a height of 56
device-independent pixels with an internal padding of 8 pixels,
both on the left and the right. Inside the container,

Row layout to organize its children.
The middle child, the

Expanded,
which means it expands to fill any remaining available space
that hasn’t been consumed by the other children.
You can have multiple

flex argument to

The MyScaffold widget organizes its children in a vertical column.
At the top of the column it places an instance of MyAppBar,
passing the app bar a Text widget to use as its title.
Passing widgets as arguments to other widgets is a powerful technique
that lets you create generic widgets that can be reused in a wide
variety of ways. Finally, MyScaffold uses an
Expanded to fill the remaining space with its body,
which consists of a centered message.

For more information, see Layouts.

Using Material Components