DAVdroid is a synchronization app to synchronize CalDAV/CardDAV collections with Android devices. It consists of two parts:
- a GUI that allows you to add and manage accounts and settings,
- synchronization adapters for CalDAV/CardDAV, which are interfaces between CalDAV/CardDAV services and the Android APIs.
Data storage: Contacts, events or tasks are stored in so-called content providers, not in DAVdroid itself. Those content providers are provided by system apps (Contacts storage, Calendar storage) or 3rd-party apps (OpenTasks).
User interface: DAVdroid is not a contacts, calendar or tasks app. It does not provide facilities to edit/view contacts, events, tasks etc.