[jQuery] Quick simple syntax question.

[Pickledegg]

In one of the tutorials on this page:

http://docs.jquery.com/Tutorials:jQuery_For_Designers

in this bit of code, (on the starred line), the 'event' is passed to
the function that toggles the .thebody class.

I don't understand what this 'event' is and why is it passed on this
line and not any of the others..

Can someone possibly explain what its there for please? thanks.

// When the page is ready
   $(document).ready(function(){
     $(".article .thebody").hide();
     $("#container .article ul")
       .prepend("<li class='readbody'><a href='' title='Read the
article'>Read Body</a></li>");

********     $(".actions li.readbody a").click(function(event)
{ *********
       $(this).parents("ul").prev(".thebody").toggle();

       // Stop the link click from doing its normal thing
       return false;
     });
   });