This lists the content object as it currently exists, and the past several iterations of that content object. You can scroll down to the version of the object and if required click on 'revert to...' link to revert to that version of the content.
This is useful if you need to look back into the history of the object to see when changes have been made, who made them, and what they were. You can also easily switch from one content block to another as your needs dictate.
You can also schedule expiration of content if you would like the revert to take place at a time you are not available.