The Page Revision Feature allows you to revert to previous versions of a page, in case the current version is broken.
In the WordPress admin dashboard, go to the list of pages/posts:
Select the page you want to revert to a previous version, then click “Edit” and you go to the editor:
In the right-hand menu of the editor, you’ll see the “Revisions” section. Click on it and see the revisions. On the top slider, you can identify the version you want to revert to (you can identify it by the publishing date):
After you’ve identified the version you want to revert to, click on “Restore this revision”: