ASP.NET MVC is not different than ASP.NET. MVC is just a framework. It sits on top of ASP.NET in order to provide better design and development infrastructure than straight Web Forms. Here is a good non-technical explanation of MVC (near the bottom of this article):
http://c6s.co.uk/?s=%22how%20to%20explain%20mvc%22&x=0&y=0[
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MVC provides a much easier way to develop loosly-coupled web applications compared to Webforms. However, that does not mean that you cannot do loosly-coupled applications with Webforms, it just means that it is harder. If you see MVC as a framework, I think you will see the benefits that it provides, just as MVVM provides benefits to WPF applications.