Hello all of you enrollment/authentication experts.  I am trying to get a handle on the new enrollment structures. 

I am assuming that by using one of these enrollments, the student is automatically enrolled in a course, so the step of entering an enrollment key is eliminated? 

Could someone explain the difference between using a flatfile enrollment and an external database?

My next questions is, how do these two work with authentication?  and, does the authentication have to be external?

Thanks for the edification,

Chardelle