Touch Keys
The Touch Keys are displayed in a bar at the bottom of all of the screens to provide easy navigation within the device software.
The Touch Keys are displayed along the right side of the screen when the phone is held in horizontal mode. If you don't see the keys, drag upward from the bottom of the screen, or drag to the left in horizontal mode, to redisplay them.
Back
Key: Tap to back up one step at a time and close on-screen
items such as pop-up messages, the on-screen keyboard, etc. Touch
and hold the Back Key to activate Dual window mode which allows you
to open two apps at the same time.
Home
Key: Tap to immediately return to the Home screen. Touch
and hold to access Google Now.
Recent Apps Key: Tap to display the apps you recently
used. Touch and hold to access available options for the current screen
or app.