SchoolTool - Using SchoolBell With iCal: "Apple's iCal application uses a simple model for sharing calendars. One person 'publishes' a calendar. Only that person can modify that calendar, and they must do so using that instance of iCal. As long as that's the case, everything works fine, and other people can 'subscribe' to the calendar, view it, and receive updates.
SchoolBell's model is more complex. More than one person can be given permission to edit a given calendar. Sometimes SchoolBell will automatically add events to a calendar, for example, when a person makes a reservation for a resource, the reservation is added to their personal calendar.