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.