This is a BETA test feature. It is subject to change. Your Calendar Sharing URL allow programs like Microsoft Outlook to display your calendar. It is a Read-Only iCal subscription format.
Please note that Google Calendar and Google Apps Calendar support reading of this format, however Google does not update this feed, nor can the feed be forced to be updated either by your or our servers. This is a limitation of Googles implementation, which we feel is a mistake on their part. Until Google adds this feature, adding your calendar to Google is useless since any changes you make to your calendar will never be updated in your Google Calendar.