can anybody explain or point to explanations of how MVC, MVP, MVVM differ?

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relevant wikipedia articles read, to my eyes, exactly the same. So how do I construct in my mind a mental model differentiating these, for both planning my projects and recognizing these patterns in other people’s work?

Also, a barely related question. I have been making a WinForms gui lately where I needed to do pretty thorough unit testing. So instead of just displaying strings in the widgets I used the notion of “screen model” (which is unit-testable without bothering about popup dialogs and the like) which then gets rendered onto the widgets as such. Of course, that is not in any sense the (domain) “model” of MVC which is a wholly different thingie. So did I just stumble upon some well-known pattern of whose name I am being woefully ignorant?

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ok, here is a nice quote from here Overview of the ModelView – ViewModel (MVVM) pattern and data-binding – Russell East's blog

MVC – The view sits at the top of the architecture, the controller sits below the view. The model sits below the controller. So the view knows about the controller, the controller knows the model. The view is notified when the model changes.

MVP – The controller is replaced with a presenter. The presenter sits at the same level as the view. The presenter listens to the events of both the view and the model and mediates the interactions between both the view and model.

MVVM – The controller is replaced with a view model. the view model sits below the UI layer. The view model exposes the data and command objects that the view needs. You could think of this as a container object that view goes to to get its data and actions from. The view model pulls its data from the model(s) below.

Yeah, nooooow I get it :-).

Are there code samples out there that would illustrate how the same thing is done “canonically” using each of the patterns and then compares/contrasts them? Or maybe, if all else fails, a cows-and-milk explanation?