David Chartier, writing for Finer Things in Tech:

Apple tells you a number of things that iCloud syncs between devices in Settings (or System Preferences) > iCloud, such as Photos, Contacts, and Reminders. But I’ve noticed a number of other OS-level things that sync between my devices (presumably through iCloud), but Apple doesn’t seem to keep a central, comprehensive list. Let’s make one.

Read the list, learn about the stuff that’s shared between devices. Good list. And if you notice anything that should be on this list, be sure to let David know.