SCV's are your city builders. But they getting annoying since they are hicks.

Marines are my favorite ground non-robotic unit for terrans. They don't require vespane gas which speeds up the process. A army of 10 can easily do alot of damage.

I will barley ever make firbats. They don't attack air and require vespene gas which means they are hard to get in a rush.

Starcraft is known for what ghosts do, Nuking. They can be cloaked and spy on the enemy but their shotguns suck. I don't use them unless im playing a big game.

Why did they create a vulture. I've seen no use for the vulture except as a scout.

If you are playing a protoss player, use siege tanks to get rid of those annoying photon cannons. Siege tanks are the long range weapon for terran. Siege most is awsome.

Goliaths are marines and missle turrets in one. They are perfect for attacking an enemy with ground and air defenses.

Wraiths are expensive and don't do damage. They are cool when you are playing a player who has ground units who cant attack air.

I love dropships. If you can fill ten drop ships when marines, you can get a nice force into an enemys base.

Science vessels are good for exploring and using there powerful tricks.

Battle Cruisers are pointless. They take forever to build, are expensive, are slow moving, and don't do much except for there Yamato Gun which is awsome.

Command centers are what they name is. They control the comming in of goods and the control over units and buildings. That is where you are stationed.

Supply Depots supply food and supplies for you base.

Refinery is like you crystals except only one scv can harvest the gas at a time.

Barracks is the building you use to create your ground units. I usely have about 5 at the end of a game.

Enginerring Bay is used to upgrade your barrack's units and allows you to use missle turrets.

Missile Turrets are great if you dont want a air-force. They scare mostly all air units from your base. They also are detectors of things around it.

If you are going to have a big marine or firebat force, a academy allows you to get better guns and stim-packs which stimulate you units.

Bunkers are the defense of your base. 4 units in their will be protected until your buker is destroyed and then your units can fight at normal health.

A factory is used to make vultures, seige tanks, and goliaths. You have to have a attached machine shop to build seige tanks.

A starport is used to create air units. They can have a control tower attached.

A science facility is used to get the ability to make nukes, make ghosts, create battle cruisers and science vessels. They can have a physics of covert lab attached.