The Terrans are a young technology species with psionic potential. The Terrans of the Koprulu Sector descend from the survivors of a 23rd century colonization mission from Earth. Compared to the Protoss and Zerg, the Terrans are highly factionalized and endure frequent wars amongst themselves in addition to the more recent conflicts with their alien neighbors.
The term Terran generally refers to the humans descending from the survivors of the "Long Sleep" and consequently to the human inhabitants of the Koprulu Sector. The term may be used synonymously with human and Terrans of the Sector may extend its meaning to encompass those not descending from the "Long Sleep".
Humans of the Earth-based United Earth Directorate refer to themselves as humans, mankind or humanity, although they are sometimes referred to as "Terrans" by Blizzard Entertainment.
The Terrans arrived in the Koprulu Sector via supercarriers in 2259, landing on three separate planets – Tarsonis, Moria and Umoja. They were cut off from Earth.
Prior to the Great War, the Terrans were primarily divided into three factions in the Koprulu Sector, each based on one of the original settled planets – the Terran Confederacy, Kel-Morian Combine and Umojan Protectorate. The Confederacy was the strongest faction.
During the Great War the Terran Confederacy, experimenting with psi emitter technology, bore the brunt of attacks by the Zerg (infested planets were frequently purified by the Protoss) while facing the Sons of Korhal. The Sons eventually destroyed the Confederacy by using emitters to summon a wave of Zerg upon the heavily-populated Tarsonis and created a new government to rule the Terrans called the Terran Dominion, ruling from the world of Korhal.
The inauguration of Emperor Mengsk of the Terran Dominion. Unknown to the Terrans of the Koprulu Sector, the humans of Earth were aware of their existence. However, no interference came from Earth until the discovery of the alien invaders, sparking panic. The new Earth government, the United Earth Directorate, dispatched an Expeditionary Fleet to take control of the sector and defeat the aliens.
After approximately six months of stability, the Dominion came under attack by the UED. The Dominion was quickly countered. However, they proved useful to Infested Kerrigan, the leader of approximately half of the Zerg Swarm, who was engaged in a civil war with the rest of the Zerg... which the UED had taken control of. Striking an unlikely alliance with Dominion emperor Arcturus Mengsk, with whom she shared an adversarial relationship, they defeated the UED forces on Korhal. Kerrigan quickly betrayed her former ally before going on to defeat the rest of the UED fleet.
The Dominion launched a counterattack against the Zerg when Kerrigan was in a weak position, but due to the damage it had taken, Mengsk was forced to assemble a coalition of "special interest groups". The attempt failed. Kerrigan allowed the Dominion to survive, however.
By the Second Great War, the Dominion was the strongest Terran force in the Koprulu Sector, vying with the Kel-Morian Combine and the Umojan Protectorate for influence. On the eve of war, Raynor's Raiders resumed its anti-Dominion campaign after a period of relative inactivity.
The Terran polities were engulfed at the start of the Second Great War by a massive Zerg invasion. Kerrigan's objective was the recovery of a Xel'Naga device, and the invasion was a way of searching for it. Billions of Terrans were killed.
Unique aspects of the Terran units include
- Marine/Marauder Stimpack (a transitive buff which increases movement speed and attack speeds at the cost of hitpoints)
- Supply Depot Lower (ability to remove pathing from a structure, useful in creating Doors and Gates)
- Siege Tank - Siege Mode (unique Morph Ability for replacing one unit with another)
- Battlecruiser - Yamato Cannon (a single target damage ability with a long casting time)
- Calldown - Mule (unique ability which spawns a unit through the Call Down effect)
http://starcraft.wikia.com/wiki/Terran for most of the text.