Flight director (FD) modes integrated with autopilot systems perform calculations for more advanced automation, like "selected course (intercepting), changing altitudes, and tracking navigation sources with cross winds.
"[1] FD computes and displays the proper pitch and bank angles required for the aircraft to follow a selected flight path.
[2] The pilot simply keeps the aircraft symbol on the attitude indicator aligned with the command bars, or allow the autopilot to make the actual control movements to fly the selected track and altitude.
When the aircraft approaches FL200 the FD horizontal bar will deflect downwards thus commanding the pilot to lower the nose in order to level off at FL200.
The exact form of the flight director's display varies with the instrument type, either crosshair or command bars[4] (so-called "cue").