I've been banging my head against the wall trying to understand these concepts for a week now. I was really surprised when I came across with a very understandable and simple explanations of these concepts in the ASP.NET MVC NerdDinner application tutorial. I suggest this to anyone struggling to have that 'aha' moment.
http://nerddinnerbook.s3.amazonaws.com/Part12.htm
It's so good that I don't have any questions and won't (fingers crossed) be buried, lol.
Hopefully it will be as helpful to someone as it was to me.