What is the Heads-Up Display?

Question

My dad put something there (chose option of 'visible only in heads-up display') and niether of us can find where it went. I have no doubt I will feel extremely stupid about how simple this probably is.

Answer 1

For a computer-related definition, check this Wikipedia entry:

"The HUD, short for Head-Up Display or Heads-Up Display, is the method by which information is visually relayed to the player in computer and video games. The HUD can be an important part of a game's user interface.

Taking its name from the real-life version, the HUD is frequently used to simultaneously display several pieces of information including the main character's health, items, and an indication of game progression (such as score or level)."

So, if you have some sort of visor or eye-piece, it sounds like you chose an optional whereby certain things will be displayed only in the visor / eye-piece and not on screen.