The Saga Continues...
StarCraft: Brood War continues the award-winning saga of galactic warfare as the Zerg, Protoss and Terrans struggle for their continued survival. With the shattered Zerg hive torn apart by fierce in-fighting, the Protoss seek to reunite with their Dark Templar brethren and begin the rebuilding of their homeworld, Aiur. Terran Emperor Mengsk I, having achieved his goal of total power over the human colonies, must now turn his attention to both the rising power of the woman he betrayed -- Kerrigan, the infamous Zerg Queen of Blades-- and a conspiracy deep within his own ranks.

    
Features:

Three all new campaigns continue the epic StarCraft storyline;

New worlds to explore, from the Dark Templar twilight homeworld of Shakuras to the blasted and barren deserts of Korhal;

Original cinematic scenes and new music tracks;

100 new multiplayer maps;

New Weapons of War:

Protoss Corsair - Support Fighter
Created by the Dark Templar specifically to combat both Terran and Zerg troops.
Protoss Dark Archon - Psionic Entity
Although physically weak, the Dark Archon is possessed with immense psionic power.

Protoss Dark Templar - Stealth Assassin
Once considered heretics, they have rejoined their Khala brethren, and are a force to be feared.
   
Terran Medic - Field Surgeon
Recent evaluations determined that healing troops in the field proved to be more cost-effective than training new recruits.

Terran Valkyrie - Missile Frigate
A modern redesign of the gunship, perfect for massed enemies or quick assaults.
   
Zerg Devourer - Heavy Strike Flyer
An extremely venomous monster, designed to cripple large enemies with a dose of corrosive poison.
   
Zerg Lurker - Heavy Support Beast
A mobile siege weapon, capable of burrowing and attacking from its underground lair.

Source: http://www.blizzard.com/us/broodwar/