From Halopedia, the Halo wiki
Specializations are higher skills that Spartan-IV super-soldiers can achieve by using armor mods and cutting-edge technology. On the UNSC Infinity, Commander Sarah Palmer requests level 50 rates in War Games. In Halo 4, Specializations are unique armor enhancements. Six specializations were made immediately available on Xbox LIVE to those who purchased the Halo 4 Limited Edition bundle while two were available with the standard game.
Specializations are unlocked after completing the first fifty levels in Halo 4. Upon unlocking specializations, the player must choose one to advance through before they can select another. Each specialization consist of rank paths which are composed of 10 levels each. Armor sets, emblems, visor colors, weapon and armor skins, and armor mods are unlocked along those paths. Armor mods work similar to tactical packages and support upgrades and, are not tied directly to a specific armor for that specialization which means a player doesn't have to wear that armor to use that particular mod.
List of specializations
The Operator specialization optimizes the operation and control of vehicles.
The Pathfinder specialization optimizes unconventional deployment within unknown enemy territory and with no assistance.
The Pioneer specialization optimizes a Spartan for deployment into unknown, hostile territory for the purpose of gathering and relaying intelligence.
The Rogue specialization optimizes a Spartan for single-operative missions which require lone deployment for incredibly long durations of time.
The Stalker specialization optimizes a Spartan for target shadowing missions while operating at close range to the target itself.
The Tracker specialization optimizes a Spartan for long-range target tracking in unconventional scenarios.
The Wetwork specialization optimizes a Spartan for stealth operations.
List of appearances