The page Intel posted is much more informative on the tech details:
http://www.intel.com/technology/io/thunderbolt/index.htm

Thunderbolt is DisplayPort and PCI Express over a single cable. Devices that attach via Thunderbolt will use the already standard PCI Express specs, and have an external Thunderbolt connector and signaling chip instead of an internal PCIe connector. And as long as the host OS has PCIe support, it can then talk to Thunderbolt devices using the same drivers that would talk to an internal PCIe card.

Pretty impressed myself. This opens up a lot of possibilities for notebook expansion, without requiring either proprietary laptop docking stations, or by requiring single expansion slots like ExpressCard. One cable to plug in and one port can now add a high end sound interface, multiple gigabit network ports, fast SATA storage And more to any notebook with the port. This will allow for a thin and light future MacBook Air to be just as expandable as the big 17 inch systems.