The Activity Feed shows a history of system activities, with the most recent activities at the top. In includes posts from other users and activities related to things you are following.

 

Use it to collaborate with your team members, the same way you would use Facebook.  If you have information to share, you can post it here and everyone on your team will see it.

 

The Activity Feed page has a small comment area at the top, with the activity history below it. When you click in the comment box, that area expands to show you additional options, shown below: