How and what benefit i can take from included Sizzle.js along with jquery 1.4.2?

Question

latest jquery 1.4.2 downloaded from jquery.com comes with Sizzle.js also.

How and what benefit i can take from included Sizzle.js?

Is Sizzle.js a standalone library?

Why it's included inside jquery library, for what purpose?

/*!
 * jQuery JavaScript Library v1.4.2
 * http://jquery.com/
 *
 * Copyright 2010, John Resig
 * Dual licensed under the MIT or GPL Version 2 licenses.
 * http://jquery.org/license
 *
 * Includes Sizzle.js
 * http://sizzlejs.com/
 * Copyright 2010, The Dojo Foundation
 * Released under the MIT, BSD, and GPL Licenses.
 *
 * Date: Sat Feb 13 22:33:48 2010 -0500
 */

while this is mentioned on sizzle.js website

Completely standalone (no library dependencies)

Answer 1

Here is the resource for that:

http://wiki.github.com/jeresig/sizzle/

Selector Features

* CSS 3 Selector support
* Full Unicode support
* Escaped selector support #id\:value
* Contains text :contains(text)
* Complex :not :not(a#id)
* Multiple :not :not(div,p)
* Not attribute value [name!=value]
* Has selector :has(div)
* Position selectors :first, :last, :even, :odd, :gt, :lt, :eq
* Easy Form selectors :input, :text, :checkbox, :file, :password, :submit, etc
* Header selector :header

Code Features

* Provides meaningful error messages for syntax problems
* Uses a single code path (no XPath)
* Uses no browser-sniffing
* Caja-compatible code

Answer 2

jQuery requires sizzle in order to function. You can take the benefit of a working javascript library.

Answer 3

Sizzle.js is a JavaScript library that implements a "CSS selector engine designed to be easily dropped in to a host library." jQuery uses it internally for its CSS selection needs. If you wanted a CSS engine and had no need for all the other JavaScript benefits of jQuery, you could use Sizzle.js separately.