Madoka nods. Pretty quickly too, since trains are something so natural to her.

"It's just like how people use cars to get around.. Except with trains you can transport a whole lot more people at once," she starts to explain, except she quickly seems to realise what the problem with said explanation might be. It makes her look slightly awkward. "Ah.. um, do you know what cars are..?"

It's possible he doesn't if he seems confused about trains as well!