PhantomJS is a headless WebKit with JavaScript API. CasperJS is a navigation scripting & testing utility that runs on top/alongside of PhantomJS.

If you’re thinking “headless WebKit??!!?”, then it might be easier for you picture PhantomJS as a web inspector console that can be injected into any web page that you want, then accessed and used.

CasperJS makes it alot easier for you to navigate around a web page testing as you go. To be fair, my explanations don’t do these two tools enough justice. Please visit http://phantomjs.org/ and http://casperjs.org/ for a better explanation and more advanced features that aren’t covered here.