This option opens the Savvy Editor window so you can edit the content.  If you do not have this button showing for your content area then either that area is not editable as defined by the template or you have not been given rights to update that content.  After you have updated and saved your content it will be shown in preview mode.  The action button will be orange and your changes are pending publication.  For detailed information about the editor, see the Savvy Editor Guide documentation.