Android Lollipop is a version of the Android
mobile operating system developed by Google ,
spanning versions between 5.0 and 5.1.
Unveiled on June 25, 2014, during the Google
I/O conference, it became available through
official over-the-air (OTA) updates on
November 12, 2014, for select devices that run
distributions of Android serviced by Google
(such as Nexus and Google Play edition
devices). Its source code was made available
on November 3, 2014.
One of the most prominent changes in the
Lollipop release is a redesigned user interface
built around a design language referred to as
" material design ". Other changes include
improvements to the notifications, which can
be accessed from the lockscreen and displayed
within applications as top-of-the-screen
banners. Google also made internal changes to
the platform, with the Android Runtime (ART)
officially replacing Dalvik for improved
application performance, and with changes
intended to improve and optimize battery
usage, known internally as Project Volta.
As of June 2015, statistics issued by Google
indicate that 12.4% of all Android devices
accessing Google Play run Lollipop. 
Lollipop is succeeded by the Android M , which
was unveiled in May 2015.