After completing a task you have access to a summary screen which has useful information.
Under the overview section you can see how many points and stars you earned; the better you play the more stars and points you receive. You can find out more about how the score is calculated here.
You also have the following additional options on the summary screen:
Keep track of your progress towards your Daily goal, replay the task by tapping on Play again or continue to the next task in the mission via the Continue button. If you liked the song you just played, you can add it to your Favorites or to your Song collection.
If you would like to compare your scores against other players, you can do so via the Leaderboards.