jQuery is a lightweight javascript library that will help you write better code faster.

jQuery is free to use, any way you like. It has a dual GPL2 and MIT style license that allows you to use it however you like.

From http://jquery.com/ "jQuery is a fast and concise JavaScript Library that simplifies HTML document traversing, event handling, animating, and Ajax interactions for rapid web development. jQuery is designed to change the way that you write JavaScript."

jQuery works across many different browsers. (IE 6.0+, FF 2+, Safari 3.0+, Opera 9.0+, Chrome) so you don't have to worry about things breaking on different browsers.

jQuery will help keep your javascript and HTML separate, which is MUCH easier to maintain.

You can download jQuery and put it on your server, or link to one of the content providors like this: <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js"></script>
( Note: hotlinking is generally bad, but it's ok in this case! see http://docs.jquery.com/Downloading_jQuery#CDN_Hosted_jQuery)

jQuery has Plugins http://plugins.jquery.com/ that can add new functions to jQuery. Anyone can write a plugin and there are thousands of them, doing things from form validation to animation.

I recommend the jQuery site or Google for finding plugins. I find tons of stuff when I Google "jQuery Graph Plugin" for example, including sites that review the different options, like http://www.reynoldsftw.com/2009/02/6-jquery-chart-plugins-reviewed/.

Note: anyone can develop plugins, so the quality and documentation varries. As a general rule, I try to stick with plugins that have good documentation.

I find this cheatsheet from Impulse Studios really helpful. http://labs.impulsestudios.ca/jquery-cheat-sheet OR Google: "jquery 1.4 cheatsheet", it's the first option

jQuery is Javascript. It's easy to forget sometimes, but you can use any functionality you could from Javascript, like string manipulation.

jQuery is Awesome!!!

Tips
Get your hands dirty! It takes a little while to get completely comfortable with jquery, but it's worth the investment of time. After this meetup, you will be able to do a lot of powerful things in jQuery. However, there is really no limit to what you can do especially when using plugins.