Not required until you reach a whole new level of Java. This essentially turns your class into a kind of task.

So, when you do "EasyTime plugin = new EasyTime();", it makes a new instance of the Main class, a new task. It then performs the stuff inside these brackets. I used this to make a custom *not hacked* client in mc, where timers etc where needed, but mostly for events I listened for! Anyway, little lesson over :D