Home Touch Buttons
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've recently used
(your open websites may also be dsiplayed). Touch and hold it to access
available options for the current screen or app.
You can choose to display your open websites in the Recent
Apps screen. From the Chrome app, tap the Menu icon 
> Settings > Merge tabs and apps (enable or disable the setting).
Swipe horizontally across the buttons to switch to Mini view (for one-handed operation).