On the phone
Still to write — what the app looks like in your hand, and what it is for.
Calendar
Your calendars on every device over CalDAV — native to the phone, owned by you.
Runs on CalDAV
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.