The compass is displayed in the upper right corner of the screen, and indicates what direction your view is facing. You are able to toggle between two different modes when you tap the compass icon.
When the compass is put into static mode, it will lock the compass and face you north. Use 1-2 fingers to rotate the view accordingly.
When the compass is put into dynamic mode, it uses the phones magnetometer to rotate the view when you physically move your device a direction.