The… Cascade?

Curious about the name Cascading Style Sheets? The Cascade is basically the method used to decide which rule wins, when multiple rules have been applied to a site.

Often the rule that 'wins' will be the one that is most specific - for example, if you want to style all <p> paragraph text in the document red, you might write:

      
      p {
      color: red;
      }
      
    

But you may have some particular paragraphs that you want to color goldenrod, not red.
Yes, 'goldenrod' is a genuine CSS color name!

HTML:

In your HTML document, you can add a class to those particular paragraphs, let's call it special:

      <p class="special"> This is not your usual paragraph, it is a little different.</p>
      
    

CSS:

You can then specify a rule for the special class in the CSS (you use a period . to address a class):

      .special {
          color: orange:
        }
      
    

Because a unique class is more specific than a generic <p> paragraph, the style for special will overrule the usual style for <p>.