Struggling to understand the meaning of this statement?

Exercise: Basic CSS: Improve Compatibility with Browser Fallbacks

Can anybody clarify what this means?

It looks like a variable is being used to set the background color of the .red-box class. Let’s improve our browser compatibility by adding another background declaration right before the existing declaration and set its value to red.

The code is:

<style>

:root {

–red-color: red;

}

.red-box

{

background: var(–red-color);

height: 200px;

width:200px;

}
</style>

<div class=“red-box”></div>

I am lost here.

Thanks for any suggestions.

I figured out the problem.