I'm still wrapping my head around the concepts, but I think the difference between views and layouts is that layouts are sort of like document templates that are common to the entire application (or to a subsystem) like headers and footers and site-wide stylesheets and javascript files and the like, while views are specific reusable pieces of display code (like outputting a single table or other HTML fragment that could appear on multiple pages within the application, or the even entire page minus the header/footer). A controller can "build" your page by assembling multiple views together.
-Carl V.