What kind of information is synced through Apple ID?

[levmc]

If I use same apple ID across multiple devices what items or info could I expect to sync?

 

[revmacian]

If I use same apple ID across multiple devices what items or info could I expect to sync?

You should be able to sync Mail, Contacts, Calendar, Photos, iCloud Drive, Notes, Reminders as well as data from apps (including 3rd-party apps) that feature iCloud sync.

 

[Minorite]

Just go to Settings > Apple ID > iCloud. You will see the list of what can be synced.