Will remind you to cast Commanding Shout if buff not present or fading in less than 5 seconds. You have to be in combat, dismounted, and have at least 10 rage to display the reminder icon.
Check my others aura for a Rampage Reminder, a Victory Rush Reminder, and a Battle Shout Reminder.
PS: Battle Shout Reminder and Commanding Shout Reminder are not supposed to be loaded together, disable the one you don't need by clicking on the WA - > Load -> Never.