Is used in action at AppBar

*/ Choose between icon Or child parameters. But not both together!/*
// icon: Icon(Icons.'AnyIcon'),
child: Text('Any Text'),

itemBuilder: (BuildContext context) => [
    PopupMenuItem(
        value: 1,
        child: Text('First),
    ),
],
onSelected: (v) => doSomething(context, v),
),

Is a flexible way to add navigation to the Application

Is a Widget that displayed at the bottom of the screen

bottomNavigationBar: BottomNavigationBar(   
    items: [
    // Use the items parameter to add BottomNavigationBarItem Widgets
        BottomNavigationBarItem(
            icon: Icon(Icons.'AnyIcon',),
            label: 'Title', // if not exists cause an error
        ),
    ],
    onTap: (value){ // Respond t user input with onTap
        // navigateToYourScreen();
    }
),

Is made from three parts

If is more than 4 or 5 items => choose one the vertical layouts