The neighbor’s daughter has a palate widener in her mouth; What is this appliance? And how does it help the alignment of teeth?

A palate widener or rapid expansion appliance is a mechanical device fixed to upper teeth. It contains a screw mechanism which gets wider as it is turned. By being connected to both sides, it can be used to widen the upper jaw. Rather than removing teeth in patients who have crowding, an expansion appliance can be used to move the halves of the upper jaw apart, effectively growing more space for the teeth. This results in a broader display of the teeth, a more beautiful smile, and has been shown to be very stable. Simply widening the dental arches through orthodontics alone forces the teeth out into the cheeks and lips and is not generally stable.