jQuery is collection of functions that you can integrate in your web pages to develop them easy.
50 #jQuery useful functions: http://www.smashingmagazine.com/2012/05/31/50-jquery-function-demos-for-aspiring-web-developers/
How to install jQuery: https://www.packtpub.com/books/content/installing-jquery
A. For beginners, a tutorial which shows you how to do your first page in jQuery: http://www.tutorialscollection.com/jquery-tutorial-a-jquery-guide-for-beginners-with-examples/
B. jQuery tutorials for Designers http://webdesignerwall.com/tutorials/jquery-tutorials-for-designers
C. All you need to know about jQuery http://www.tutorialspoint.com/jquery/
In our days each application you should be used on both web and mobiles platforms. This article tells you why you should use jQuery mobile: http://www.creativebloq.com/jquery/five-reasons-use-jquery-mobile-4135691