The Home Touch Buttons are displayed in a bar at the bottom of all of the screens to provide easy navigation within the device software.
Back Button: Tap to back up one step at a time and close on-screen items such as pop-up messages, the on-screen keyboard, etc.
Home Button: Tap to immediately return to the Home screen. Touch and hold it to access the Google Now shortcut.
Recent Apps Button: Tap to display the apps you recently used as well as all of your open websites. Touch and hold it to access available options for the current screen or app.