The Home button takes you to the Home screen and provides other convenient shortcuts. On the Home screen, tap any app to open it.

The Home button at the bottom of iPhone

See apps you’ve opened. Double-click the Home button when iPhone is unlocked. 

Use Siri or Voice Control. Press and hold the Home button. S

On iPhone 5s and later, you can use the sensor in the Home button to read your fingerprint, instead of using your passcode to unlock iPhone or Apple ID password to make purchases in the iTunes Store, App Store, and iBooks Store.  If you have iPhone SE, iPhone 6, iPhone 6 Plus, or later, you can also use the Touch ID sensor for authentication when using Apple Pay (in countries where Apple Pay is supported) to make a purchase in a store or from within an app. 

You can also use the Home button to turn accessibility features on or off.