Click on  Notifications tab at the left Menu:-

1.  Red notification indicates the number of new notification you have
2. These are the actions when notifications will appear:
   1. When admin uploads new session
   2. When some leaves comments on the session
   3. When some leaves comments on discussion board you have commented
3. View button will lead you to specific items the notifications is related to for eg if notification is related to a particular session it will lead to particular session.