From Joomla! Documentation
The Content Dashboard is accessed via the icon to the right of the Content menu item. It is a square of four squares. The dashboard contains three panels corresponding to the three subsections of the Content menu. These panels cannot be edited or unpublished. The dashboard may also contain additional panels with information about the site. New installations show Popular Articles and Recently Added Articles. You can add more panels by selecting the + icon in the vacant Add module to the dashboard panel.