On page load show something with ::before

The backgrounds or lines about where will be text or box or something. I saw it on YouTube still on big company sites? What is that exactly? And how its made?

Thanks.

Could you try to explain what you mean, maybe with an example?

When load page in a white background then where will be the text but the page still not loaded display there a background color with padding.

youtube.com

?

So display with a color line or backgroud line where will be text

I think perhaps what you are referring to is something called preloading. Try googling terms -

website preloading screen

Here is a codepen example: