eGroupware GroupDAV use for

Hello !
Could someone explain me how groupDAV application in egw can be used for ?
Is it only to sync adressbook with apple client ?
I’ve already used SyncML egw capacity to sync with outlook calendar ; is there a possible way to use groupDAV to sync the egw calendar too ? Because groupDAV is designed to sync calendars, tasks, adressbooks.
Best regards, hope someone could answer me,
Ed