Website Folding/Overlapping-Effect with Scrolling

I've recently noticed that the website building tools provider wix.com uses a great folding-effect for their homepage. When you scroll down, the hero-image moves up and the section below appears to be static, but once the hero image moved all the way up you can just start to scroll the usual way. I tried quite a lot but couldn't find a proper way to get the same result. How can this be done? How do the elements need to be positioned and how can you manage to scroll one section and only afterwards start to scroll the rest of the page? Thanks!