jQuery is simply a way of Write less, do more.It is designed to change the way that you write JavaScript.

jQuery is a fast and small JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid and simple/easy web development.

jQuery is a cross-browser JavaScript library designed to simplify the client-side scripting of HTML

jQuery’s syntax is easier to navigate a document, select DOM elements, create animations, handle events, and develop Ajax applications.The approach to the jQuery framework allows the creation of powerful and dynamic web pages and web applications by writing very less.

Unique features of jQuery:

• DOM element selections using the cross-browser and traversal and modification
• Events Handling
• CSS manipulation with very smart function
• Effects and animations by just single function
• Ajax (no need to create objects)
• Extensibility through plug-ins
• Cross-browser support (works well in all browsers)

How can you do, is very simple include a file in your page.

<script type="text/javascript" src="jquery.js"></script>

You can get/download this file by jQuery CDN or Google CDN.

The links from where you can go are
http://ajax.googleapis.com/ajax/libs/jquery/1.6.2/jquery.min.js
http://code.jquery.com/jquery-1.6.2.min.js

The most popular and basic way to work with jQuery is to use the .ready() function.

$(document).ready(function() {
// function body will go here
});

Or

$(function() {
// function body will go here
});