Alright, I\'m confused by all the buzzwords and press release bingo going on.
Flash is a Runtime Environment - you use the Flash Authoring tool to make some Flash content, and the Flash player processes your content, executes the scripts, and draws the appropriate pictures onto the screen.
Flex is a Development Framework - you use the Flex development tools to define how your component-based content should work, and then Flex generates the Flash content for you. You could have made the same thing with the Flash Authoring tools, but using Flex may let you avoid reinventing some wheels.
In functional terms, Flash is an extremely versatile runtime; it gives you lots of freedom to do anything you want. But if you're building a loan simulator, you probably don't need the freedom to define precisely how all the pulldown menus and screen transitions work. Probably you'd rather that you could just use premade components for that stuff so you can concentrate on the loan stuff. Flex lets you do that, with the cost that it may turn out to be a lot of work if you decide that you do need a lot of freedom to change all the fine details.