Solel//dev docs

Contacts

Contacts keeps your own address book and one the whole household shares, and lists everyone with an account on your server. Mail and Calendar use the same contacts, and your phone can keep them in its own Contacts app; see Phones and laptops.

In Contacts

The household address bookYour own contacts, the household's shared book and the people on your server, and who can see and change each.Importing contactsBring contacts in from iCloud, Google or Outlook with a vCard or CSV file, and take them with you.