Solar Exposure Lite shows the seasonal path of the sun in the camera view of the app.
Red is the path at the winter solstice, green at the spring/fall equinoxes, and green at the summer solstice.
The solar path depends on your latitude, which is provided by the devices GPS. The accuracy of the displayed path also depends on the direction of view. Hold the device up, aim parallel to ground, and tap "Re-calibrate" in "Setup" mode until the map display matches your surroundings.