When a user follow your calendar, the users calendar program stores an unique URL which the calendar program request a couple / up to many times each day.
If the users calendar program requests your calendar, the user is actively following ...
An explaination of some of the keywords on the statistics page.
Active followers
The number of active followers. The users calendar program must have made a request to your calendar for updates within the past 30 days.
Total followers
The number ...