Workspaces generate notifications for personally relevant activity and general activity.
Activity is defined as when someone comments, replies, likes, gives points or tags people in a superhchat or assignment widget.
When someone interacts with something you have interacted with, it is considered personally relevant activity. An example of this is you replying to a comment which then gets more replies. This will generate a personally relevant notification for you.
All activities that do not directly concern you or anything you have been part of fall into the general category.
New containers or widgets on a page do not create notifications. If the admin wishes to inform participants of these types of changes it is recommended to send an email inviting the user to visit and look at the new content.