The Selection Prompt widget is special form of SelectionBox, which allows you to retrieve the answer to a simple question.
No action is taken until the "OK" button is pressed.
For more information, consult XmSelectionBox(3X) in the OSF/Motif Programmer's Reference Manual.
NOTES
In Motif 1.1, you could add a single Work Area child widget to a Selection Prompt in order to provide some extra functionality. In Motif 1.2, you can also add a MenuBar and multiple PushButtons.
The buttons in a Selection Prompt are gadgets and so will not highlight when selected.
If you want to change the labels of the built-in buttons, they should be changed in the Selection Prompt resource panel, not in the resource panel for each button.
See also: