These tabs in the Dashboard present lists of content by type for pinpoint editing. If a tab includes a number highlighted in red, that indicates the number of items of that type which are not currently live (this is especially useful for picking out comments which have not yet been moderated).
To edit a specific content element, click the "Edit" button for its row.
Live? Whether the content is currently "live" (visible to users who are not logged in or logged in with Reader privileges).
To edit the content in full, click the "View" button for the row--this will open the page for that item. Then, click the "Edit" button at the bottom to edit as normal.
To permanently delete one or more content elements, check the checkboxes for each of the relevant rows in the content list and then click "Delete selected content".