While you may not need them all the time, revisions can be very useful if you need to reload an older version of a post or a page, or see what you wrote in a previous save. If you don’t see the revision box on your edit screen, you will need to turn it on in the screen options. By default it will be located under your content editor, but this can be moved to wherever you wish. Regardless of whether or not you have the revision box on your page, any past changes you have made to your content will be seen here.
WordPress makes a new revision every time you save a draft, publish and update currently published content as well as periodical auto saves. Clicking any of your past saves will bring you to the revision comparison page. Alternatively, you can click Browse next to Revisions in your Publish box.
Use the Previous and Next buttons to navigate your revisions as well as dragging the slider to the timeline. In the main window, you can see the changes that have been made to your content with the items highlighted in red are the before and the ones highlighted in green are the after.
Clicking Restore This Revision will restore the content highlighted in green. By default, this only compares consecutive revisions. If you wish to say compare your current save with a save that is further back, check the box next to Compare any two revisions. This will split your slider allowing you to compare any two revisions on the timeline.
In order to restore the older version, you will need to move the slider on the right to the position of the one on the left and click Restore This Revision. This will take you back to the edit page where you can update and publish your content.