The Head-Up Display (HUD) is a transparent display that presents navigational data without requiring the pilot to look away from his usual viewpoints.
In most cases it displays airspeed, altitude, a horizon line, heading, turn/bank and slip/skid indicators. In some aircraft (the Boeing 787, for example) the HUD displays data from guidance computation for low visibility take-off and low visibility approach, coming from the same flight guidance computer that drives the autopilot.
The HUD is not a default equipment in our flight simulators software. But it can be present in some addons.