What is the Back button on Android?
The Back button appears in the system navigation bar at the bottom of the screen and is used to navigate in reverse-chronological order through the history of screens the user has recently worked with.
Why did Android Remove Back button?
Google acknowledged that gestures don't work for all users. It added that gestures are harder to learn and takes some time to adjust. It also admitted that gestures can interfere with the way people navigate the app. Google also revealed that Android users love the Back button and is used 50% more than the Home button.