jQuery is a cross-platform JavaScript library designed to simplify the client-side scripting of HTML. Used by over 60% of the 10,000 most visited websites, jQuery is the most popular JavaScript library in use today. jQuery is free, open-source software licensed under the MIT License.
W3Schools has many examples of JQuery and how to use it.
W3Schools Tutorial on Jquery
The official JQuery site has a Learning Center
jQuery Part #1 http://www.mcpressonline.com/web-languages/techtip-jquery-fundamentals-part-i.html
jQuery Part #2 http://www.mcpressonline.com/web-languages/techtip-jquery-fundamentals-part-ii.html
http://www.mcpressonline.com/general/creating-an-interactive-information-screen-in-a-browser-is-it-possible.html