Display and set/change a thumbnail image of the feature/post thumbnail attached to the Post/Page/Custom Post Type when viewing posts/pages in the All
This shows the Thumb column in the All Pages/Posts admin view and in this case a thumbnail is available and shown. There would be a blank space if no thumbnail was found for the post or page.
If the column is not showing in your All Posts/Pages view this shows you where you can check to see that the "Thumb" column is selected to be displayed
Shows the change icon located next to a featured image/thumb indicating it can be changed inline without having to edit the content item first