New Analytics Output: "Content Type" what is "course.discussions" vs "course.discussions.discussion"?

[mikeg]

I'm trying to see if students bother to look at the responses I give on the discussion board after their participation deadline.  As a result, I've exported the course activity via 'New Analytics'.  In the "Content Type" column of the csv file I download, Canvas differentiates between "course.discussions" and "course.discussions.discussion". 

At first I figured "course.discussions" were when students created a new thread on a discussion board, but it seems like they actually correspond to course announcements, but there already is a 'course.announcements' Content Type. 

Can someone clarify what these terms mean or direct me to an appropriate guide?

Thanks!