Every page in the Drupal backend, whether a basic page or a news story, lists five tabs at the top:
The View tab allows you see what your page looks like. It is the default tab when you first navigate to a page in the backend.
The Delete tab allows you to delete a page. Keep in mind that if you delete a page, it will be gone forever. You can preserve the content on pages and still hide them from public view by switching them to drafts or archiving them. Learn more on the publishing and drafts webpage.
The History tab allows you to view a page's publishing history. You can see when a page changes from a draft to being published, published to archived, etc. In the image with the maroon buttons below, you can see an example of the publishing history where the page was saved as a draft, then later published.
The Revisions tab allows you to review past changes you made to a page. Here, you can also revert a page back to one of its previous versions by clicking the "Revert" button next to the version you prefer.
This tab appears when you change a published page to a draft. It allows you to preview the most recent draft copy. For more clarity on what happens when you revert a published page to a draft, see the publishing and drafts page.