event Keyword .. what does it really do ? why is it used in Jquery .

event Keyword .. what does it really do ? why is it used in Jquery .

Picked this example from the Jquery Docs of on function : 

What really would happen without the event keyword(Marked in red) in the code below : 

  2. $( "p" ).on( "myCustomEvent", function( event, myName ) {
  3.   $( this ).text( myName + ", hi there!" );
  4.   $( "span" ).css( "opacity", 1 ).text( "myName = " + myName ).fadeIn( 30 ).fadeOut( 1000 );
  5. });
  6. $( "button" ).click(function () {
  7.   $( "p" ).trigger( "myCustomEvent", [ "John" ] );
  8. });
got the example from here :