Earn Stars by playing Hidden Object Scenes. In each scene, you can earn up to 5 Stars by playing the scene over and over.
As you earn more Stars, the following things will happen:
The Adventure Scene at the end of the chapter unlocks
New decorations and buildings unlock in the shop
New areas of Orchid Island can be uncovered
Also, when you earn a new Star in a scene, you will be awarded a Star Box containing valuable items. Every fifth Star Box you receive is a special 5-Star Box, but earning those requires some extra effort.
The amount of Stars you have earned in each scene can be viewed in the Scene Browser. The total Stars you've earned in the game so far can be seen in the top part of your screen when viewing Orchid Island.