Hi @AnitaCunningham,

In Canvas, all enrollments are to a section, and sections essentially belong to a course.  So in short, there is no enrollment in a course directly, it's enrollment in a section of a course.  When assigning things, "everyone" does mean just that, it's all students in all sections of the course.  If you add a second "assign to" for the same assignment, you'll see that "everyone" becomes "everyone else", which tried to ensure that all students get all of the things in the course by default (you can generally remove "everyone else" though if something is only for a specific section of the course.

I hope this info helps you out!

-Chris