On the phone
Still to write — what the app looks like in your hand, and what it is for.
Contacts
Your address book, served natively to the phone over CardDAV, held on your machine and nobody else's.
Runs on CardDAV
What it does
Still to write.
On the server
Still to write — which sidecar backs it and what that process is responsible for.
Both ways
Still to write — this app inside Officer, and the same app on its own home-screen icon.