(Combination of the words: Window and Object. Used to presents dynamic content in your screens.)
Service Studio 6.0 Help
The Widget Selector, in the Web Screen Editor, displays the path from the outermost widget to the widget currently selected on the Web Content Canvas, showed up as a pressed button in the Widget Selector.
Use the Widget Selector to select a widget in the hierarchy and easily navigate up and down in the widgets.
The picture below displays a web screen with a selected Expression widget.
Once a widget is selected, you can manage its properties in the Property pane of your workspace.
Web Screen Editor | Widgets