This dialog is accessible through menu Edit / Revert.
When choosing that menu option, the dialog appears with the book and chapter selected that is now opened in the editor.
Bibledit displays all the dates and times that a changes was made in that chapter.
If you double-click on a revision, or press Enter, then the dialog shows the changes that will be applied to the current text if you were to revert to that revision.
Text that will be inserted is shown in bold, and text that will be deleted is visible in
in strikethrough.
If you press button OK, Bibledit will revert to the "previous text".