Reworded the subscriber introduction

Author: javiereguiluz

cookbook/event_dispatcher/event_listener.rst

@@ -113,9 +113,15 @@ Creating an Event Subscriber
 ----------------------------
 
 Another way to listen to events is via an **event subscriber**, which is a class
-that can define one or more methods that listen to one or various events. The
-event priority can be defined for each method (the higher the priority, the earlier
-the method is called). To learn more about event subscribers, read :doc:`/components/event_dispatcher/introduction`.
+that defines one or more methods that listen to one or various events. The main
+difference with the event listeners is that subscribers always know which events
+they are listening to.
+
+In a given subscriber, different methods can listen to the same event. The order
+in which methods are executed is defined by the ``priority`` parameter of each
+method (the higher the priority, the earlier the method is called). To learn more
+about event subscribers, read :doc:`/components/event_dispatcher/introduction`.
+
 The following example shows an event subscriber that defines several methods which
 listen to the same ``kernel.exception`` event::