what is this 'now' mean in jquery css function
<p>I'm a newbie to jquery, I came across this in jquery api about animate() function. Even though its perfectly working, I just want to know what it mean there and how it can be implemented in some other places. Here is the example code block and urls. Thanks in advance.</p>

<pre><code>   step: function( now, fx ){
    $( ".block:gt(0)" ).css( "left", now );
   }
</code></pre>

<p><a href="http://api.jquery.com/animate/" rel="nofollow">http://api.jquery.com/animate/</a></p>

<p><a href="http://jsbin.com/ihukob/1/edit" rel="nofollow">http://jsbin.com/ihukob/1/edit</a></p>
