Question on self maximising and closing flash animation

Scenario:
Consider an HTML page, say index.html. The page has some image and text in it. When the user visit this page a flash animation should popup and play full screen and it should automatically close after giving the introduction. Now the user should see the index.html once again. The flash is basically a type of introduction. I have seen this in many webpages.

My question is Is this done in flash itself or using javascript?
That is, Is the maximising and closing of flash done using javascript or can the flash do this itself?