It uses solid state storage and the RAM, graphics system, etc. is bundled into the single System-on-a-chip. Plug in the power then hook it up to keyboard/mouse/monitor and you are up and running.
One will still need to add a powersupply and case at a minimum. (And then you can plug in your power, keyboard/mouse/monitor, etc.)
Edit: it looks like it comes with a power adapter, so it's effectively a fully functional computer out of the box (just as much as any system without kb/monitor).