Current desktops have two levels of modularity: a PCIe bus connected to the motherboard which various things are plugged into, and then a set of special components (like CPU and RAM) that get plugged into the motherboard directly. This is different in that it makes the PCIe bus the interface for all components, and the "element" housing the CPU and RAM becomes just one more thing that plugs into it.

In theory this makes tasks like upgrading the CPU easier, since you wouldn't need to deal with things like the old and new CPUs using different sockets; you'd just pull out the old Element and plug in a new one, the exact same way you upgrade (say) your GPU.

There are (in theory) downsides too, of course. If the CPU moves into a sealed package, for instance, your options for cooling it are going to be limited to whatever fans/etc. come on the package; you wouldn't be able to buy and use beefier third-party coolers, the way you can now since you have direct access to the processor. That's not a huge issue for most people, but if you're an overclocker it'd be a serious pain point.