Well i just started from zero...it say phew all my hearts are gone. What is that supposed to mean?? What are they for?
If you do a lesson you start with three or four hearts available. That means that you can make three or four errors before you have to redo this lesson.
And the encouragement comes from the fact, that you get extra point for every heart left at the successful end of the lesson.
No worries globetrotter, I don't care much for the points either. But it might be some encouragement for others. You can also see it as indicator how good you are. The more hearts you have left at the end of the lesson, the better you are, although sometimes still some hearts are used up by "wrong" errors, when you discover the next bug in duolingo and can send them your correction.