iCalendar is a computer file format which allows Internet users to send meeting requests and tasks to other Internet users, via email, or sharing files with an extension of .ics. Recipients of the iCalendar data file (with supporting software, such as an email client or calendar application) can respond to the sender easily or counter-propose another meeting date/time.

Basically, iCalendar puts ticket information in your calendar so that you can get a visual idea of what is on your plate.

If you click Subscribe to iCalendar you will be subscribing to that user's work history in the form of tickets in your mail program calendar (Outlook, Thunderbird, etc.). You will see entries in your calendar for each ticket that is assigned to the user that you have subscribed to. For example, if you have a ticket due on Friday you will see a calendar entry for Friday giving you brief details about the ticket. It is a way to manage work load and monitor other tech's work load.