It is about a prisoner, and the nature he can see was so limited, everytime he looked at the window, all he can see was just a part of the sky.He's surrounded by guards,he witness what's happening inside a jail.Despite all of that he still believe that there's a chance to live free,,, 

and as a teacher,,i'll tell my students how good their life will be if they are freely living,and despite of all the challenges that they'll encounter,there's still a chance and there's no reason to give-up...just be strong...Worst thing is to be a jail to others life..