I would like to know about that too. I'm confused as well.
It basically means the same thing. Estimated date of confinement vs estimated date of delivery.
So which is my real due date then?
Whatever date your doctor is currently going by.
When you found out you were pregnant they calculated your due date based on the first day of last menstrual cycle, since you have had an ultrasound they know a more accurate due date by measuring the baby and what stage your at.