What does $ do when using JQuery?
<p>I am reading JavaScript and JQuery, The Missing Manual</p>

<p>and they start of with this Snippet : </p>

<pre><code>$(document).ready(function(){});
</code></pre>

<p>I know that <code>function(){}</code> is an anonymous function, and that document is an object with properties I can set / read, and that ready() is a JQuery function defined in the library, but I don't know what the rest of the syntax is for and it is not explained in the book.</p>

<p>Particularly,</p>

<pre><code>$(document)
</code></pre>

<p>Can someone explain what this does or point me to a link?  Also, someone said that you can identify JQuery by this alone, is this true? </p>
