...
Audience is one of the key options of the Announcement Feeds application.
It has been added so that administrators could independently decide which group of users should be recipients of announcemenets.
This is important during creating announcements that only affect developers, graphic designers, PMs or any other groups.
If selected announcements are to reach all users, there is the "Public view permission" option, which speeds up the process of adding all user groups.
...