jQuery is javascript library, that allows users to develop dynamic web pages easily. Through jQuery, you can easily use the AJAX features in your website and you can easily apply the animation features easily.
Difference between jQuery and Javascript:
Javascript is scripting language where you can do client side scripting, where as jQuery is Framework or application developed using javascript. You can easily create animated effects by using jQuery.
Advantages of JQuery:
jQuery is light weight as compared to other Frameworks.
You can easily develop rich animated website easily with less number of lines code as compared to javascript.
jQuery is easy to learn.
jQuery has various plugins for your needs, even you can develop your own plugin easily by using jQuery.