Explain the Course Activity Stream, is this different from the Global Activity Stream?

The Course Activity Stream shows you all of the recent activity from a single course. This is different from the Global Activity Stream, which you see in the Dashboard when you first log in to Canvas. In both the Course Activity Stream and the Dashboard, you can quickly reply to Discussions without linking to them first. As an instructor, you have the option to show the Course Activity Stream as your Course Home Page or not.
Use the Course Activity Stream to:
Quickly reply to student Discussions and Announcements without entering the courseSee what has happened since the last time you logged in.