What is a Broadcast receivers ?

A broadcast receiver is a component that does nothing but receive and react to broadcast announcements.
 For example, announcements that the timezone has changed, that the battery is low or that the user changed a language preference.
 All receivers extend the BroadcastReceiver base class.

 Broadcast receivers do not display a user interface. However, they may start an activity in response to the information they receive, or they may use the NotificationManager to alert the user like(flashing the backlight, vibrating the device, playing a sound)