In your case it is an object passed to your css function.

myObj={} // a blank object

Here you can use this too

myObj={'float' : 'right'}

xxx.css(myObj);

Here is another example of object

var myObj={

    'varOne':'One',

    'methodOne':function(){ alert('methodOne has been called!')}        

}

myObj.methodOne();​ // It will alert 'methodOne has been called!'

A fiddle is here.