The News Feed makes it easy to stay on top of all class activity. It includes ALL class activity such as added comments, new work, critiques, responses to lesson discussions.
It keeps track of what you haven't read, and let's you quickly cycle through each notification using the arrows on top, next to the News tab.
The most recent of this also appears on 'Class Home' at the bottom under 'Class News.'
While News Feed is great for seeing ALL of the class activity, Personal Notifications only show activity that is directly related to you, from all classes and communities of which you are a part. It contains activity related directly to your contributions.
You can find these in the "Personal Notifications", located in the top navigation bar. Items you haven't read yet will be highlighted.