Terrans

The heart and soul of every Terran assault
The Terrans originally were banished from earth for long forgotten crimes. Now they fight for their survival in a strange galaxy filled with unknown dangers. The Terrans have flying buildings which can be moved from
one location to another. Their units range from the basic marine to the powerful battlecruiser. They also have the cloaking device and the scary nuclear bomb.
Protoss
The most powerful of the basic units
The Protoss are humanoid beings who have developed their psychic abilities to perfection. They use their innate psionic abilities and combat skills to defeat all who
oppose them. To make up for their lack of numbers, these guys have very powerful units compared to the other races. They also have High Templars who when transformed into an Archon can easily annihilate any enemy who unfortunately happens to be in its way. Regenerating plasma shields protect every Protoss unit(and building) thus making them very hardy in combat. They also are the most technologically advanced race.
The Zerg
Reminiscent of the aliens in ALIENs,no?
Many different species actually, comprise The Zerg. They remind you of those nasty creatures in the movie Aliens. Their sharp teeth and lethal claws can easily penetrate any armor and make mincemeat out of their enemies. What is unique about this race is that all their units(except flying units) can burrow on the ground and hide. When burrowed, these fierce creatures cannot be seen or attacked unless a detector is nearby. All Zerg units come from larvae which a Hatchery produces non-stop. Because of this non-stop production of larvae, the Zergs can easily win a war by overwhelming the enemy with their great numbers.