The Command Center is a store for all of your minerals and vespene gas. Here you can build a SCV (or more) if you like. This building is very important as it is the building to which your SCVs will return with the gathered minerals and vespene gas. Without this building you won't be able to work up the minerals and vespene gas into buildings and units. WARNING! This building can be infested be the Zerg Queen. The Zerg will then be able to build Infested Terrans, a suicide Terran, which deals 500 hit points of damage.
The Comsat Station or the Nuclear Silo can be attached to this building.

The Supply Depots store all of your supplies. Without these buildings, you won't be able to build more than a few units.

This building is build upon a vespene geyser. When build, you can use your SCVs to gather the vespene gas for other units and buildings.

In this building you can train your Marines, Fire Bats, Ghosts and Medics. This building is required if you want to build a Factory.

The Engineering Bay is used for a couple of purposes. First of all it is in this building you can upgrade your infantry weapons and armor. Next it gives you the ability to build Turrets for air defense.

Here you can upgrade your Marines with the U-238 shells for longer shooting range, the Stim Packs for faster Marines and Fire Bats and you can upgrade your Medics abilities. It is required to build Comsat Stations and to train Fire Bats, Ghosts and Medics.

This building is great for defense. Build a bunker, put 4 men into it, and those men won't be hit until the bunker is destroyed. The men can still shoot when they are in the bunker, but you can't use their special abilities.

This is the ultimate air defensive building. Shoots with two anti-air Longbolt Missiles dealing 20 hit points of damage. It's just a pity that the building is too easy to destroy.

The Factory is where you build your vehicles. This includes the Vulture, the Siege Tank and the Goliath. To the Factory you can attach the Machine Shop, where some of your vehicles can be upgraded. See the Machine Shop description below.

No army is without some kind of air support. The Terran uses the Wraith, the Dropship, the Science Vessel, the Valkyrie and the Battlecruiser as their airborne units. These can be built here at the Starport. You can attach the Control Tower to this building.

It is very nice to have some vehicles and some aircraft, but it is much nicer if they can be upgraded. This is done here. The vehicles' weapon damage and armor together with the aircraft's weapon damage and armor can be upgraded here. The upgrade prices are listed below.

The Science Facility is the high-tech Terran facility. This building is required to build a Science Vessel. In this building you can upgrade the Science Vessel abilities. Furthermore, you can attach the Covert Ops or the Physics Lab add-ons to this building for upgrade purposes.

This is an add-on to the Factory and is required by the Siege Tank. In this add-on some upgrades can be done to the Vulture, the Siege Tank and the Goliath. See those vehicles under the unit section for descriptions of what the upgrades do.

The control Tower is an add-on to the Starport. This building is required if you want to build Dropships, Science Vessels, Valkyries and Battlecruisers. At the Control Tower, some things for the Wraith can be upgraded. See the Wraith description to see what the upgrades do.

The Ghosts require this add-on to be built. The Covert Ops is an add-on to the Science Facility. Upgrades for the Ghost can be found in this add-on.

The Battlecruiser requires this add-on to the Science Facility. Some upgrades for the Battlecruiser can be found here.

The Comsat Station is a useful add-on to the Command Center. Using its special ability - Scanner Sweep - reveals a large area where the ability is used. This also reveals hidden/cloaked units. This ability only reveals that area a couple of seconds. The ability uses 50 energy points.

Where do you store a nuclear bomb? In a Nuclear Silo of course. This add-on to the Command Center can hold one nuclear bomb. The Ghost launches the bomb. The Ghost must be close to the target. The nuclear bomb is a very devastating bomb. It deals 1000 hit points of damage to its target, and has a large area effect, dealing lesser damage to buildings not as close to the target.