what does ::before really do?

Question

So I read the docs and probably understand the purpose of ::before and ::after. If my understanding is correct, they should always work in combinat

Answer 1

::before and ::after are pseudo elements as you can see on this example:

CSS:

.container-fluid>p::before{
    content: "HI";
}
.container-fluid>p::after{
    content: "Bee";
}

http://jsfiddle.net/vX2jW/ You can read more here: http://css-tricks.com/almanac/selectors/a/after-and-before/