Terran Overview

Terrans are, in my opinion, the best race in the game. All of their units are pretty versatile, since the main land unit (the Marine) and the main air unit (Wraith) can attack both air and ground targets, making either one capable of holding off an attack. Most of the Terran Buildings can fly, which can help if you get caught by an early Zergling rush; just lift your CC, and you are saved. Also, after an attack, you can repair units that are almost dead, saving you lots of resources, as well as time, in the long run.

Mobile Buildings
Like I said before, most of the important buildings (specifically, Command Center, Barracks, Engineering Bay, Factory, Star Port, and Science Facility) can lift up and move to another location. This can be very helpful. If you are attacked, you can move your buildings to another location without losing them (you still lose addons, though). Also, when expanding, you can build a CC and then fly it over, but that is kinda slow. Another tactic is to fly a Barracks behind enemy lines and start building an army near the enemy base; using the tactic correctly can be devistating.

Critical Building Damage
Terran buildings, like the buildings of the other two races, go from green to yellow to red. However, Terran buildings, once in the red, continue to lose hit points until it hits 0. Once it gets to 0, boom, you're dead. This can be an advantage when attacking Terrans; just attack until the building is red, then move on. As long as the building isn't repaired, it will die.

Addon Buildings
Some of the Terran buildings can be expanded through addon buildings. These addons can either allow you to build certain units, like Ghosts, or give you access to certain abilities, like Control Towers. When the building lifts off, the addon is left behind. If you come upon an enemy addon, you can drop your building next to it and take it over.