This terminal can be used to access certain armor unlocks, emblems, and XP bonuses based on the terminals in the game you have accessed and which Spartan Ops missions you have completed.
It may seem like random guessing, so I'll give a pic of some of the completed codes.
- Raider Shoulders: Complete LandGrab
- Raider Chest: Complete SniperAlley
- Raider Helmet: Complete The Challenge