As the name implies Announcements allows you to announce something to all users of the Panel. This feature can be accessed through the Admin Panel → Administration → Announcements.
You can create different type of Announcements, which determine their color. Content is the message itself, which has a maximum limit of chars.
After creation of Announcement, you can Resend it to all users again, edit or delete it.
Announcements are displayed at the bottom left of the Panel, under the Notifications.