The Revisions screen shows any backup copies of your post or page. Each time you save a draft or Update, a revision is saved. WordPress.com will store the last 25 revisions for each post or page on your blog. Revisions allow you to look back at the recent changes you’ve made and revert to an earlier version if necessary.
To find the Revisions screen, you will need to click on ⚙ Published or on ⚙ Draft Saved to bring up the access to revisions and other useful settings.