where autocomplete come from for MAC MAIL

in Mail on my MBP and my Mac Pro i have a database accessible from Windows > Previous Recipients that contains emails that i responded to on my two computers. i can /add/ each of these manually to my Contacts database which i have available to all my devices via Mac Contacts using iCloud.

is there such a thing as a database like this in iOS6? when i respond to an email on my phone am i correct in thinking there is no way to get this into the autocomplete or does it AUTOMATICALLY get added to some kind of Previous Recipients database that only resides on my iPhone?

TIA