Why is used after multiple floating DIVS in a container DIV?

Question

I have encountered a

at many places, but I am not aware why is it done? Can someone brief me on this, why it is used in

Answer 1

All technical details has been introduced above. More generally this kind of element serves as 'hard line' for floated elements, laying them properly vertically one under another. It's worth to say that there are better methods these days.