As you do this you'll earn Flowers, and they will help you unlock new chapters and scenes.
Buildings are special decorations that require time and some materials to construct or upgrade. Materials can be collected from Star Boxes and are sometimes awarded as bonuses for playing Hidden Object Scenes. Each building you construct will require materials and some time to complete, but once it's been completed, it will generate Coins every so often. You can use these Coins to decorate even more!