OK, please bear with me as I know I am going to be asking stupid questions...
I am still on Lion, and I believe I do have an address book app (was it removed in Mountain Lion?):
rpg% ls -d /Applications/Address\ Book.app
/Applications/Address Book.app
But I don't seem to have a "Contacts" app.
rpg% ls -d /Applications/Contacts*
ls: No match.
I see that in Mountain Lion Address Book.app has been renamed Contacts, but even so, there seem to be two different mechanisms for syncing: one in the preferences for Contacts.app and one in system preferences.
iCloud offers to sync contacts, but I don't know what these are. Contents of Address Book.app? Something else?
Does anyone know what the difference is between these two mechanisms?
[I have tried syncing address book with google mail's contacts, using the Address Book preferences, and the results are extremely bad. A lot of my contacts are invisible in Address Book, because they have lost their names (they are indexed under the Organization header instead. 😮)