How to create a moving image with css/jquery/html

I am hoping to find out how people make the background of the section/div of their website move when scroll.

An example of what I am talking about is like this:

http://ift.tt/1zvPeFo

I am not quite sure how to explain it, sorry. I have tried background-position: 50%;, background-attachment: fixed;. But I have still had no luck :(

Thanks in advanced,

Kieron