jQuery.noConflict() has one simple purpose: it enables you to load multiple instances of jQuery on the same page—typically different versions of jQuery at that. You may be wondering why you would ever want to do that. There are two primary reasons. First, you may want to use a jQuery plugin that is not compatible with the newest version of jQuery, while writing most of your jQuery code on the newest version of jQuery. Second, you may have no control over what jQuery version is loaded on a page, and you need to be sure a specific version of jQuery is loaded for your jQuery code or jQuery plugin to work (such as is the case when developing public WordPress plugins). Regardless,
jQuery.noConflict() can address these concerns for you.