There was more than one model of personnel carrier. Some were enclosed on all sides except the roof, and others were open on all sides, able to seat two rows of personnel back to back. They transported passengers and cargo around various Alliance installations, and were occasionally used in combat.
During their occupation of the Great Temple on Yavin 4 prior to the Battle of Yavin, the Alliance made use of the open-sided carriers to shuttle pilots and other personnel around the base. During the evacuation of Echo Base in 3 ABY, Rebel transport ships were loaded using troop carriers with enclosed sides. A personnel carrier of this model brought the Rebel strike force to the captured Lambda-class shuttle Tydirium inside the main hangar of the Home One, prior to the Battle of Endor.