According to
jQuery's website:
"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."
Their motto is "Write less, do more" and they definitely achieve that. What it does is allow you to use jQuery's functions, events and properties merged with (or instead of) the standard javascript code to offer more powerful features which handle issues such as error-checking, cross-browser bugs and such for you. Because of this, your code is easier and faster to write, more thoroughly tested, and more extensible, without the need to write your own library of tools.
jQuery sits on top of javascript, extending the features without replacing them. You can use a mixture of standard javascript and jQuery in the same page seamlessly.
