JavaScript has a large, respected place in the modern web. From simple beginnings at NCSA, it's now an integral part of modern web applications, whether for UI, Ajax, or other needs. It has official specifications and is constantly evolving, making working with JavaScript ever more exciting. Working in concert with HTML and CSS, it can do much more than simple interactivity, and it can easily communicate with (almost) any backend system. Its purpose is to give us more than static pages—we want pages that do work. If you coded along, we made a simple Ajax application, and while right now the commands are probably nonsensical to you, you can hopefully see that JavaScript is fairly legible. We'll be taking a deep dive into JavaScript's grammar and construction later on.
We haven't spent time discussing the backend use of JavaScript yet, but don't worry—that's next.