How do I make sense of Bontrager Tire Models?
They are indicators of what product line Trek is placing each tire in. For example, R=road, AW=all weather, t=Touring, XR=cross road (or something like that, indicating smaller tread that is not too big for mixed road riding) G=gravel and so on. I would say that these prefixes don't really mean much, just choose a tire that is appropriate for the type of riding you will be doing.