Well going one JSP to another JSP page... or one PHP page to another PHP page - is the common HTML web application mindset which is premised on "pages". Server side pages more specifically...
To go one from one MXML "page" to another MXML doesn't quite translate in that context. A key thing to note is that Flex applications are pure client side. At a basic level Flex application, is one "binary" if you will (a Flash swf file)... so you could go from one Flex application, to another Flex application - not advised however.
So within your Flex application you'll have various visual components that you can control what show's and when either programmatically, or using something called states. In the book we have one chapter on application navigation, and another chapter on using view states. Flex comes with something called navigator containers (e.g there's a tab navigator that let's you put a bunch of tabs up at the top and the content changes depending on which tab you click on).
Another popular navigator container is the ViewStack (
http://j.mp/icGfVQ).