Are you ever using your iPhone with just one hand and can’t reach an app button to open it. Simply double tap (not double press it is a lighter action) the home button and the screen moves it down. See the image below. I found this out cause I kept thinking I had a problem with my iPhone, as I must be a secret double tapper. Not sure I’ll use it much as I can simply ask Siri to open the app but at least now I know why it happens. Want to turn it off? Go to Settings – General – Reachability.