Widget

• A Widget is description of part of UI on the screen.
• A Widget is a way to declare and construct UI.
• A Widget is not just a piece of UI , it might display something, it might help define a design, it might help with user interactions. For example Padding is a Widget, Margin is a Widget, Center is a Widget, Layout Row and Coloumn is also a Widget.
• Widgets are arranged into a tree of parent and child Widget.
• Widgets are nested each other.