HQ/SUPER HQ/SUPER DUPER HQ - Used as the Green HQ, don't let it be destroyed, or it will result in a catastrophic Mission Failure.
Garage/Super Garage - Your vehicles are built here.
Resource Depot - Plastic is taken to here from destroyed buildings or units where it will be recycled again. As well as from object laying around the battlefield. Energy is also returned here from object found laying around like flashlights. Resources are carried here by dumptrucks with lasers attached to them.
Guard Tower - Used to defend your base from oncoming enemies. That try to get into your base or destroy you. Fires one steady stream of bullets at enemies in the vicinity. Also creates a barbwire fence connecting from guard towers that are nearby it. Guard towers are the most common defensive buildings.
Pillbox - Another building used to defend the base by being offensive or defensive similar to the Guard Tower in style. Basically there is a gunner or two inside that shoots at oncoming enemies. While being protected by a barrier wall. The gunner is actually part of the building but basically that is a pillbox.
AA Gun - This is a anti-air defense turret which protects the base from enemy helicopters and paratroopers. They basically shoot down any enemy aircraft that comes near the base. In order to stop from aerial attacks being a problem to your base. They do not have any real effect though on ground units attacking you.
Barbed wire fence - Used to defend your base. Keeps enemy from being able to enter through that location in which you place the fence. Until of course being destroyed in which they will be able to get past then.
Acid Gun - Used to defend Colonel Blintz.