What is the "star" for on the Activity Feed?

The "star" icon  located on the Activity Feed is there to be used for motivational purposes.

When the Educator clicks on the "star" icon in acknowledgement of the student's real-time success, the student will receive a notification on their student dashboard just below 'THINK Points to Spend' that a 'star' has been received from their teacher.  

For further information on the Activity Feed, please see Motivation through the Activity Feed.