Armory
Required to upgrade vehicle and ship weapons and armor and also needed to build Thors.
Barracks
Trains infantry.
Bunker
Almost identical to its StarCraft counterpart, the Bunker has received a boost in HP and two permanent upgrade options for singleplayer only; capacity increase (from 4 occupants to 6) and a mounted auto-turret. Note that capacity may vary depending on which units are stored, while a marine only takes one space, a marauder will take two spaces, limiting the ammount of marauders in one bunker to 2 or 3. When not needed it can be salvaged for 100 minerals.
Command Center
The Command Center still serves the role it played in the previous game. It has received the ability to carry up to five or more SCVs inside. In addition, the add-on system from StarCraft has been eliminated; now, Command Centers must be upgraded, and cannot be downgraded, converted, or salvaged afterwards.
Orbital Command
This immobile upgrade of the Command Center increases its sight range and enables scanning of troop movements through the fog of war (same as Sensor Sweeps in the first game). It can also call down MULEs to assist SCVs in mining, and increases the supply capacity of Supply Depots.
Planetary Fortress
This immobile upgrade of the Command Center greatly increases its power and grants it weapons to attack enemy ground units. Cannot take on air however.
Engineering Bay
Required to build Missile turrets and upgrade infantry.
Factory
Builds hellions, Goliaths, Vultures, Siege Tanks, Diamondbacks and Thors.
Fusion Core
Formerly known as the Anti-matter Core and the Deep Space Relay, this structure allows production of Battlecruisers and provides research options.
Ghost Academy
This structure enables Ghosts to be produced and provides research options for them. In addition, it stores Nuclear Missiles for launch. Nukes do 300 damage and a 200 extra to buildings.
Missile Turret
The Missile Turret still detects cloaked and burrowed units and now launches two missiles. This turret can also fire cluster missiles when upgraded.
Refinery
Unchanged from StarCraft, other than a reduction in HP from 750 to 500.
Starport
Deploys air units. Takes 50 seconds to build compared to the Factory and the Barracks which both takes 60 seconds.
Has more health than Barracks and Factories.
Supply Depot
The new Supply Depot can submerge, enabling troops to walk over it. It is smaller and can be made into an important part of Terran base defenses, preventing enemy units from walking past them.
Sensor Tower
This structure can detect enemy units at long range, even within the fog of war.
Add-Ons
In StarCraft II, Terran add-ons work quite differently. There are only two add-ons which have been described, the Nuclear Reactor and the Tech Lab. Instead of being specific to an associated structure, each add-on can be added to any Terran unit-producing structure (Barracks, Factory or Starport), granting a specific benefit. One structure may only have one add-on attached to it, so it cannot benefit from the Reactor's bonus and the Tech Lab bonus simultaneously.
Reactor
When added to a Terran structure, this doubles the number of units produced from a building. (For instance, adding one to a Starport will enable it to create two Vikings at the same time).
Tech Lab
When added to a Terran structure, this enables the production of "higher tech" units. For instance, adding a Tech Lab to a Barracks will allow it to produce Medics, while adding one to a Factory will enable it to build Siege Tanks. The building serves the role of Machine Shops and Control Towers from StarCraft.
Tech Reactor
The best structure when it comes to building high tech units. It can build 2 battlecruisers at one starport etc.
Perdition Turret
Lowers into the ground when not attacking. Pops up to burn any ground unit that goes near it. It does not do good against Protoss units.
Psi Disrupter
Slows down all zerg ground units.
Hive Mind Emulator
Mind controls any zerg units except Drones.