Why does my iPhone 6 home screen move down when I rotate my finger on the home button?

Thanks for the help

Go to a phone shop

It's to make it easier to touch the top of the screen with one hand. I like it but to turn it off go to settings, general, accessibility and turn off reachability.

This is a mode for helping for 1 hand use usage

Its not rotating your finger that does that, its double tapping it. That's called Reachability to make 1 handed use of the phone easier.