The armored personnel carrier (APC) is an armored terran vehicle used for transporting infantry. It is a fully enclosed, wheeled vehicle that can hold up to a dozen passengers plus a driver. 
During the Guild Wars the Confederate Armed Forces equipped their APCs with reactive armor. The Kel-Morian Combine pieced them together from various materials, sometimes the same reactive armor, other times they welded metal plates to their flanks, angling them to deflect bullets. These APCs were frequently armed with double-barreled gauss cannons.
The APC's visual design was inspired by the shuttle from District 9.
The "militarized colonist transport" was an unused variant of the APC in the game files. It is camouflaged and mounts a larger turret with twin chemical/napalm sprayers. It was to appear in the Char missions of Heart of the Swarm, where it would use its weaponry to melt the remaining zerg.