It is kind of to-do-list app .But this is more simple than that.
Y.T.T means "Yesterday","Today" and "Tomorrow", so you only need care about very few things. Or we can say you just take yesterdays items as reference, and take more time think about what we need to do today. If you like you can also make a plan about tomorrows work. And thats all.
My target is that making a app easy to use, and match peoples habit, just like you draw or write on a paper with a pencil.