Revision Information

If Create new revision is checked, the site will automatically save each version of a page when you make edits to it. You have the option of including a Log message to note what your revision included. If no Log message is included, the site will save the date/time and username of the revision.

create new revision. log message. an explanation of the additions or updates being made to help other authors understand your motivations

See Revisions for additional information.