$emit , $on , $broadcast

$emit

• It dispatches the event name upward in the direction & notify to registered rootscope listener
• The event transverse upward towards all root scope and calls all the registered listeners .
• The event will stop propogating if any of the listeners stops it.

$broadcast

• It dispatches event name downwards to all child scopes and notify the rootscope listener.
• The event transverse downway and notify all the registered listeners.
• This event cannot be cancelled

$on

• It listens to event of given type. 
• It catches the event dispatched by $broadcast and $emit