CS5.5 feature Flash Builder integration

On adobe website it is described as this:
** Flash Builder integration**

  •                 Create and open projects  in either Adobe Flash® Professional or Flash Builder™. Roundtrip code  and synchronize project settings between both applications*
    

I would like to know exactly what does it mean. Does anyone have a good example of that. Does this mean i can use Flex to create UI and flash for app.