Tiers of Technological Achievement
From Halopedia, the Halo wiki
Tier 0: Transient
Tier 1: World Builders (Forerunner)
Tier 2: Interstellar (Covenant)
Tier 3: Space-Faring (Human)
Tier 4: Space Age (Humans c. 2000 CE)
Tier 5: Atomic Age (Humans c. 1940 CE)
Tier 6: Industrial Age (Humans c. 1600 CE)
Tier 7: Preindustrial (Humans c. 0 CE)