After spending a few minutes browsing the site, I still don't get how it works. The JS makes sense, but what happens on the back end to save the edited content

After spending a few minutes browsing the site, I still don't get how it works. The JS makes sense, but what happens on the back end to save the edited content? How does it work with "any CMS"? As a web developer, I don't need an explanation of how "magical" this it is to be able to edit on the page, but I do need to know how it works! If you're targeting this at developers, the well-designed CTAs and screencasts matter less that a simple explanation of what's actually going on. I don't need to read that I can "quickly integrate" -- I just want to know the exact details and make my own judgement.