You can add files to your article and this window let's you display the list of those documents. If a document is a mp3 file, you can add a player to the list to make that file playable. This is a simple window that sometimes comes in very handy.
If you are an experienced in HTML, CSS and have some programming skills, you may edit the templates for you site. Just add /_module/website/themes/editor to you site address to get to the Cornerstone CSS-editor.