Hello @Bill_C - I have made use of the Daily summary for many years as an instructor. And it works exactly as worded: I receive one email at the end of the day (for me, just before 6:30pm ET) and that email contains the title of the observed course element, along with a link that goes directly to that item in the course. I've recently updated my notification settings so that I receive immediate notification of new submission comments. That way I can reply to students and they can advance with their learning the same day.
I do not care to receive notifications about discussion replies so I leave that disabled.