Our system automatically save 7 recent revisions of your post by default. This feature help you can restore or compare the changes between revision posts. If at least two revisions exist, you will find a Revisions option in the Publish meta-box, click Browse

In the Revisions page, you can drag the button on timeline to select a revision and click Restore This Revision button to restore it. By checking the Compare any two revisions checkbox, you can compare the differences of any two revisions.