I've noticed that every event I create in my calendar is duplicated and I found out today that it looks like I have something called Exchange as well as gmail set up in my calendar settings on my iphone. What exactly is exchange? Is this something to do with Microsoft? I don't ever recall setting it up. I only recall clicking 'add account' in 'settings' on the iphone and adding my gmail accounts If it is a duplicate from my gmail I will just delete it. Just curious what exactly it means and what the advantage is to having it. appreciate the help.