javascript syntax $
<p>i'm reading a javascript source code , and i haven't written javascript before. i'm confused about some syntax of it. </p>

<pre><code>&lt;script id="source" language="javascript" type="text/javascript"&gt;

$(function () {    

 window.onload=function()
 {
mkAjaxObj(0,0);
 }    
});

&lt;/script&gt;
</code></pre>

<p>could you tell me , why the anonymous function is putted in the $( ), what is the use of $( ) , is the anonymous function will be called ? or will be execute automatically.</p>

<p>another one :</p>

<pre><code>var plot = $.plot($("#placeholder"),
          [ { data: monkeyavgtime, label: "monkey average run time"}, { data: monkeymixtime, label: "monkey shortest run time" } ], 
          {
              series: {
              lines: { show: true },
              points: { show: true }
              },
              grid: { hoverable: true, clickable: true },
              yaxis: { min: 0, max: maxtime },
              xaxis: {ticks:[[0,version[0]],[1,version[1]],[2,version[2]], [3,version[3]], [4,version[4]],[5,version[5]],[6,version[6]]]}
          });
</code></pre>

<p>1 : $.plot , what $. stand for ?</p>

<p>2 : $("#placeholder") 
    there is a tag in the html :
    
    <br>
    dose $("#placeholder") is a reference to it ? but 
    is there any different with 
    var obj=document.getElementById("product") ?</p>

<p>thanks very much !</p>
