Question

I spotted this (to me) curious css style in the default Site.css file of an ASP.NET MVC project:

.text-box.multi-line
{
    height: 6.5em;
}

Is .text-box.multi-line just the name of a class that happens to have a dot in the middle of it, or is this a nesting of two classes? Or is it something else entirely? Can you explain?

And can you provide a usage example?

Edit

Thanks for all the answers. This seems to be an omission from the w3schools css reference page.

Answer 1

it matches an item with both classes, ie.

<textarea class="text-box multi-line"></textarea>

It will not match if the item only has 1 of the classes.
It will match if the item has those two classes plus additional ones.