A teleporter is found in 2 places in both LOA, and Braike. They are the men in cloaks by the hovering cirtaglaphics found distant parts from eachother.
In other maps such as Draco, Python, or Dennebe, there is only one teleporter - Usually found in the rural, safe areas.
The teleporters are used to switch between maps without having to run back and fourth, in case, saving a heap of time.