iPhone 6 home button

[ztirffritz]

I'm using a new to me iPhone 6 and I've stumbled upon a quirk. I've found that if I swipe down on the home button it swipes down the icons on the screen and in some apps it seems to swipe the app down as if to expose something but there's nothing there. Am I missing something? What is the intended function of this 'feature'?

Ok, it seems it's not a swipe necessarily, but just double tapping the button does it.