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.
Pale, pils, Munich, etc are all 2 row barley. The difference is in the kilning. Maris Otter is a 2 row barley variety that can be killed to produce different malts.
I am no maltster, but I have used a lot of malt over the years. As I understand it, there is 2 row and 6 row malt based on the kernel alignment on the stalk (and having different specifications between the two as base malts, such as diastatic power, nitrogen levels, etc…). Typically from there the maltster adjusts its process to arrive at the final lovibond to create the maltsters categorization of malts. This would typically be the categories mentioned by Brew Bama. Pils is usually very low (below 2 L) through Dark Munich (Light Munich might be at around 4-6L, or so, Dark at 8-10L, as an example.) I had a Viking Extra Pale that was 1.7-1.9L, which is down in the Pils range. Due to its makeup, 6 row typically has more enzymatic power than a comparatively similar Lovibond 2 row variety.
I could be wrong on any of the foregoing, but at this point in my life, I am starting to forget things that are not essential to the hobby. I am just happy to get good results.