The Scrolled Text widget is a scrolled window which contains a text widget. Thus a Scrolled Text is not a widget but a compound object consisting of a Text widget and a Scrolled Window: the Scrolled Window provides a viewpoint into the Text widget.
For more information, consult XmCreateScrolledText(3X) in the OSF/Motif Programmer's Reference Manual.
NOTES
The Scrolled Text has some internal default callbacks associated with the Scroll Bars - you are advised to leave the scrolling behavior well alone.
Ensure that the Edit Mode resource for the Text widget is Multi-Line editing: the behavior of a single line Text widget in a Scrolled Window is undefined.
See also: