On the maps are several Control Points which you are to capture by repairing them. When such a point has been captured your team will gain 1 capture-point per second, each map has its own points requirement for winning the game, the more control points you capture the faster you reach the requirement and win the game.
The Hand of Nod as seen on the map DOM_Hand_of_Nod. It is a Single Player building type and has several elevators and stories to battle on :)