HTML defines the structure of a web page by using page elements as the building blocks. However, HTML by itself can not produce web page interactivity, that’s where JavaScript comes in.

Below, we see a post-it with a typical stick figure on it. We can think of this as the HTML, with the head, body, and limbs as the elements on the page:

In web development, CSS provides the style to our HTML structure. Below, the stick figure is now dressed in a nice tuxedo:

If HTML and CSS provide structure and style in this analogy, JavaScript provides interactivity, allowing our stick figure to move. Below, the stick figure moves, swaying up and down, thanks to JavaScript:

Web programmers use JavaScript to make web pages dynamic and interactive. This powerful scripting language is encapsulated in its own HTML element: the <script> element. You can think of this <script> element as the door to JavaScript for HTML. This lesson will dig deeper into what the <script> element can do for your websites and best practices on how and where to insert JavaScript in your HTML files.