Please use this tag for questions related to on-screen Navigation Bar.

With Android ICS 4.0 and the Galaxy Nexus, Google ditched capacitive/physical keys in favor of an on-screen navigation bar (aka navbar). Since then, apart from the Nexus devices, only some Motorola and Sony handsets use on-screen buttons, which have the distinct advantage of being fully customizable, provided you use some custom ROM.

Android ICS default navbar