This is applicable only URCap nodes with an HTML based UI.
When adding an item to a SelectDropDownList, this is the generic Object type.
If this Object (i.e. a new class of yours) implements the Translatable interface, the shown name in the dropdown will be the returned String from the getTranslatesText( Locale locale ) method.
For Swing based nodes this is default Java functionality.
Just @Override on toString() for the object you add to the JComboBox.