The top part of the screen is an emulated HSI (Horizontal situation indicator) . The yellow needle is the course select pointer, the moving part in the middle is the course deviation indicator (CDI) which displays the deviation (+/- 12 degrees) from the selected radial or course to or from the selected waypoint. Unlike on a real HSI where the orange heading bug is used to set a course for the autopilot, the heading bug displays the bearing to the selected waypoint. Also the HSI does not display magnetic heading but the track of the aircraft.