Attract mode
What an arcade cabinet does when nobody has fed it a coin: plays itself, shows the high-score table and begs for attention.
A cabinet sitting idle in an arcade makes no money, so even 1970s machines looped a title screen, the score table and a short demonstration of the game itself. Pac-Man introduced its ghosts one by one, with names and nicknames. The demonstration was rarely driven by real AI; far more often it was a recorded sequence of button presses fed into the game's own logic.
That only works if the logic is fully deterministic. Doom played recorded demo files on its title screen, and when a later version changed something in the physics, old demos would start walking into walls — same input, different world. Home consoles inherited the mode wholesale, long after nobody needed coaxing to put anything in.