I'll stick with some references that make it clear (diagrams and examples help when looking at patterns):

http://geekswithblogs.net/dlussier/archive/2009/11/21/136454.aspx
http://nirajrules.wordpress.com/2009/07/18/mvc-vs-mvp-vs-mvvm/
http://www.apexa.net/Blog/web_design_Blog_20090112.aspx
http://amirrajan.net/Blog/mvc-vs-mvp-vs-mvvm
http://www.dotnetfunda.com/articles/article830-comparison-of-architecture-presentation-patterns-mvpscmvppvpmmvvm-an-.aspx

And in case you are concerned about being questioned about it all:
http://www.wiziq.com/online-class/292867-design-pattern-mvc-mvp-and-mvvm-interview-questions

>To be honest I do not find that answer, which is short enough to fit in a tweet, particularly helpful. For starters MVVM has been around longer than WPF or Silverlight and MVC has been around longer than the web, at least as most of us know it. Early 70s, right? In any case it does not explain the difference between the two.
>
>Would anyone more knowledgeable like to give it a try? I am not looking to pick holes in replies, just a general understanding. Thanks.
>
>>MVC is used most often for web apps. MVVM came out of WPF/Silverlight and is generally used there.
>>
>>>What is the difference between them? Should we have a preference? It would be easy to guess MVC, which dates from the 1970s, is out of it, but that might not be accurate. Is one on the rise and one on the wane or is it more complex than that?
>>>
>>>I am hoping for an intelligent discussion among geeks.
>>>
>>>Mike