Terminals
From Halopedia, the Halo wiki
Terminals are secret places in halo 3.If you find all terminals in the game, you get an achievement.Not much else is known about terminals in halo 3.However, in the Marathon Series, terminals are the places where you can save your progres in the game.That is also the reason that the achievement you get when you find all terminals in halo 3, is called "Marathon Man".
