The leave calendar is a feature where you are able to see who is on leave at a specific date. If you're a manager this will help you view all of your staff who are off work at the same time, for how long, and how many leave requests are still outstanding, ready to be approved/declined. If you're an employee this will you know who is off work in your team at any given day.
Click the following link to watch a walkthrough of the leave calendar: Leave Calendar