Modeling Instruction in Physics: Uncertainty About My Certainty

I'm supposed to be doing my reading right now, but I keep thinking about something from class.

Lindsay asked a question in class today about what the models are, and I felt comfortable that I knew the answer. And then Laura and Bryan said that in some ways, they're still figuring out what the models are.

Does that mean I really have no idea?

To me, the models are generalized forms that are fundamental to a bunch of situations. So the first model is an object moving with constant acceleration. (I'm considering an object with constant velocity as just a special case of that.) The same equations, graphs, motion maps, verbal descriptions, etc. apply to a ball rolling down a ramp, the pen you dropped, a fan cart on a track - the specifics vary, but there is a sameness to all of those situations. The generalized sameness is the model.

Now, I can't put a name to all of the models, and the paragraph above might be about as clear as mud, so if we're going by the truism you don't really understand it until you can explain it well, I guess I don't understand. But I sure feel like I do.