This is a feature included in jQuery API v 1.0+. I have noticed this when I was working on multiple select boxes which has to do the same job on its onChange event. When I noticed that the code seems a bit ugly -

$('#start_time').change(function(){        showTimeDiff();});
$('#end_time').change(function(){        showTimeDiff();});

Then I implemented Multiple Selector feature to avoid the repetition of showTimeDiff() function call

$('#start_time, #end_time').change(function(){        showTimeDiff();});