A big part of the appeal of jQuery is that it allows you to elegantly (and efficiently) find and manipulate HTML elements with minimum lines of code. jQuery supports this via a nice “selector” API that allows developers to query for HTML elements, and then apply “commands” to them. One of the characteristics of jQuery commands is that they can be “chained” together – so that the result of one command can feed into another. jQuery also includes a built-in set of animation APIs that can be used as commands. The combination allows you to do some really cool things with only a few keystrokes.
The jQuery library also works well on the same page with ASP.NET AJAX and the ASP.NET AJAX Control Toolkit.
Visual Studio figures out external script references, such as to JQuery, by following special reference comments it finds at the top of .js files:
/// <reference path="jquery-1.2.3.js" />
For intellisense support for JQuery you need to install this Hotfix.