Not all notifications appear on the lock screen, particularly if you turn them off. Plus, like mrapplegate said, it shows your calendar.Can anyone explain why we want the notification center on the lock screen? All our notifications appear on the lock screen anyways and we can swipe into them.
The Today section has a very small summary of today and tomorrow (if you have those enabled) and then an actual piece of your calendar that shows the upcoming 4-6 hours from the present. So, if you don't have anything happening in the next 4-6 hours or so, you won't see anything there, in the actual calendar section (although you should still see a today and/or tomorrow summary, if you have those enabled).