Armitage, 35, is Zimmer's imposing bodyguard. He has little to say and will defend Zimmer to the death. Of course, this is because Armitage is actually an android, of the same class as the replicant they are searching for. Armitage has the same schedule as Zimmer; he sleeps in the same room and eats the same food - not because he has to, but because he's been programmed to replicate human behavior as closely as possible.
Seemingly human, Armitage is in fact one of Dr. Zimmer's many androids, created in 2242 at the Institute in the Commonwealth, a region to the north of the Capital Wasteland that was once the commonwealth of Massachusetts.
Armitage will stay standing next to Zimmer until the quest The Replicated Man is completed.
In the quest The Replicated Man, Armitage only has one or two lines of dialog and none of any consequence to the quest storyline as he is little more than Zimmer's bodyguard.