Panel 1: A while later, we find John at a hobby shop looking at a display of model trains. Having noticed the longing look in his eyes, the salesman (who I'll call Jasper Creosote) asks John if he needs help.
Panel 2: John waffles a whole heck of a lot when he tells Jasper that he's sort of thinking about maybe starting a hobby and is somewhat interested in electric trains.
Panel 3: Jasper turns into a sort of evangelist for life on the HO scale when he tells John that no sir, electric trains are not merely a hobby. John stupidly sets up the punchline by asking him what he thinks they are.
Panel 4: Jasper smiles broadly when he says that they're a way of life.
Summary: They're also a means by which Lynn can spend the next eighteen years or so mocking Rod for having a hobby that distracts him from what he's supposed to be doing (standing around looking stupid waiting for her to need him) and also diverts attention away from her by making him far more interesting than an antisocial hermit living in a bunker.