There is a surprising lack of information on the website. Here are a couple links that help fill in the gaps.

"elementary OS is a Linux distribution based on Ubuntu. It makes use of a desktop with its own shell named Pantheon,[2] and is deeply integrated with other elementary OS applications like Plank (a dock), Midori (the default web browser) and Scratch (a simple text editor). This distribution uses Gala as its window manager..." http://en.wikipedia.org/wiki/Elementary_OS

"elementary OS Freya vs elementary OS Luna - What's new?" https://www.youtube.com/watch?v=1CBS6RDLTNA

It looks intriguing. A host of application level services built on linux leads me to think of this as a KDE-like effort to remake the desktop.