JavaScript is a code language used to create user interfaces that often combine graphic animation and functionality. It's used on the web and in applications that run on your computer. The Mac's dashboard widgets, for example, are powered by JavaScript. If you've seen animated slideshows, fancy drop-down menus or pop-up log-in windows on a website, you were probably looking at Javascript in action.

Javascript works well with HTML and PHP so, for website purposes, it's a sexy way to add functionality and movement to a website. However, too much Javascript on a single web page can cause conflicts that lead to functionality failure. Many out-of-the-box modules/widgets/plug-ins (3 web words that mean the same thing) that enhance the functionality of a CMS are built with Javascript.

Javascript isn't easy to learn but any competent web developer should be able to install a Javascript module and make minor modifications to suit your needs and the look-and-feel of your project. If you're considering a developer and that person has zero knowledge of Javascript, said person is wrong for the job.