Though commonly referred to as ‘2-row’, 2-row and 6-row are types of barley. It’s like wolves and domesticated dogs: they are both in the canine family. 2- and 6- row are in the barley family.
I believe what Denny is driving at is that the 2-row type is processed differently (i.e. malted, kiln dried, etc..) to various stages such as Pils, Brewer’s malt, Xtra Pale, Pale, Pale Ale, Lite Munich, Dark Munich, Vienna, etc. Following the canine example; a certain dog, such as a German Shepard, can be processed (aka trained) to be a guard dog, a seeing eye dog, a police dog, a sheep herder, etc.
Maris Otter, Golden Promise, Haná, Chevalier, Full Pint, Copeland, etc are specific breeds of ‘2-row’. Again, with the canine example; various dog breeds are German Shepards, Chihuahuas, Great Danes, etc.