Safari marks certain webpages as SnapBack pages. When a page is marked for SnapBack, you can quickly return to it after opening other webpages.
If you open a page by typing its address in the address box, or if you go to a page and then choose History > "Mark Page for Snapback," the page becomes the SnapBack page. The SnapBack button (orange circle with a left-pointing arrow) appears in the address field to indicate that a page has been marked as a SnapBack page.
When you use the search field to search the web, a SnapBack button appears in the search field so you can easily return to your search results.
To return to a SnapBack page, click the SnapBack button.