1.It doesn’t use HTML .It cannot reload the page after it is once loaded.
2.It is a combination of several technologies like CSS,HTML,DOM .
3.It is accessed in proper procedure to retrieve data from server.
4.Heavy Use of AJAX often leads to server overload due to more number of connections created.
1.It focuses on the interaction with HTML elements.
2.It cannot provide new functionality by combining with other technologies.
3.jQuery does not require understanding of the complete procedure to setup a page.
4.There is no chance for overload of server while using jQuery since there is no such heavy usage in jQuery.