iCal should be used only for permanent dates in conjunction with Address Book–birthdays, anniversaries, holidays, or any event that occurs every year on the same date. For this, it will ultimately serve as your read-only Master Calendar, where all your calendars are merged alongside your entries made in either your iPhone or gCal. The complete sync layout looks like this – iPhone <=> gCal -> iCal – with gCal acting as a channel to wirelessly sync your iPhone entries to your iCal entries.
iPhone and gCal have 2-way sync capabilities with each other. An update made on one will be made on the other
iCal has only 1-way sync capabilities. Updates made in iCal will not be made in your iPhone nor your gCal
via INSTRUCTIONS: How to 3-Way Sync the iPhone, iCal, and Google Calendar – Calendar Help.
