In the early days of the internet nearly all pages viewed were designed with paper documents in mind. Think of what they did as turning physical articles — into a digital ones. To do that however; all they needed was some text and a small bit of markup.

Nowadays, we have evolved into beautiful,functional,web-applications. You wanna know a secret? HTML is at the base of both what we did way back when that is still in use today. HTML is in essence what the browser-engine uses to read the ‘structure’ of your page.

Think of it this way - we may have some HTML like this <h1>HelloEarth</h1> in other words…JUST some HTML. Say we’d like to color that heading green. In this case we could sprinkle in some CSS using the HTML style property. Something like <h1 style=”color:green;”>HelloEarth</h1>would result and the browser-engine would look at the HTML for structure and interpret the CSS also.

Long story short, the HTML provides a set of rules and structure that is required to develop a web-page. CSS provides a set of rules and structure that is used to style markup. JavaScript provides a set of rules and structure that is used to enhance functionality of markup. I’m sure others could add similar for back-end languages of their choice.