Announcements
The Announcements screen contains a listing of the last 36 - 48 hours worth of announcements, this includes minor details such as Bug fixes, it may also include major changes.

The major announcements are typically sent as a Global Notice to your status window and will appear when you login, or the next time your status is displayed if you are playing when the message was sent, however if you miss an announcement or wish to view all the announcements from the last day or so this would be the place to do it.