Alright, I\'m confused by all the buzzwords and press release bingo going on.
Flex is a framework FlexBuilder is an IDE (in an attempt to resolve the confusion between the 2, adobe is renaming FlexBuilder to FlashBuilder)
if you do not know what a Framework is:
Flex is to Flash as what CodeIgniter is to PHP
or like what .net is.
I like to think of a framework as extending a language like you would extend a class in OOP.